acid + metal

When you add an acid to a metal you expect a chemical reaction to occur in which you produce a salt and hydrogen gas.
Your teacher expects you to be able to write a word equation to describe this chemical reaction.
AUS-e-TUTE has just added a new tutorial, game, test, and exam to help you write word equations for the chemical reaction between an acid and a metal.
AUS-e-TUTE Members should log-in to use these new resources.
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Formula for Hydrogen?

I admit it. I love TV game shows. Last Friday I watched one of my favourite shows while eating my (late) lunch. I was even moderately successful at answering some of the questions, until the Host asked The Chaser what the chemical formula for hydrogen was. This led to the following exchange:
Chaser: H
Host: Incorrect
Contestants: H one (we will assume they meant H₁)
Host: Incorrect. The correct answer is H two (we will assume he meant H₂)

So, who was right?

Let's take the Host's "correct" answer first.
The Earth's atmosphere contains small amounts of diatomic molecules of hydrogen gas. "Di" means two and "atomic" refers to atoms so hydrogen gas in the atmosphere is made up of molecules in which 2 atoms of hydrogen are bonded together. When we make hydrogen gas in the laboratory we are making these H₂ molecules. So it seems that the Host got it right ..... except ..... the question didn't ask for the formula of hydrogen gas found in the atmosphere!

So let's turn our attention to the Contestants' response.
Is H₁ a plausible chemical formula for hydrogen?
Not really. If there is only 1 atom of an element in the chemical formula, the "1" is trivial and not included in the formula, so H₁ is the same as H which was the Chaser's response!

So, was the Chaser right?
Is H a valid chemical formula for hydrogen?
Hydrogen is a strange atom. It has 1 proton in its nucleus, and 1 electron "orbiting" that nucleus. In fact, this 1 so-called "valence electron" is a feature common to all Group 1 metals (alkali metals), but other properties of hydrogen suggest it is more like a non-metal than a metal. This similarity to the Group 1 metals led to the prediction that it should be possible to create metallic hydrogen. This would be a solid in which the hydrogen atoms (protons in effect) would be held in a 3-dimensional array with delocalised electrons acting as the metallic bonds holding the array together. This metallic hydrogen would, in theory, be an excellent conductor, indeed it would be a "superconductor", which is why the race has been on to create it!

A chemical formula of a covalent molecule tells us how many atoms of each element are covalently bonded together, H₂ has 2 atoms of hydrogen with a covalent bond between them.
But the chemical formula for a 3-dimensional metallic array refers to the ratio of atoms of each element, if only 1 element is present in a metallic array, like that of sodium metal, then the chemical formula is just the symbol for the element, Na, in this case, or H if you are referring to metallic hydrogen.
So, H is a valid chemical formula for metallic hydrogen, if it exists.
But does metallic hydrogen exist?

In January 2017, researchers at Harvard University announced that they had produced metallic hydrogen in the laboratory using immense pressure. So metallic hydrogen, H, can exist.

Back to the game show.
The Host was right, H₂ is the chemical formula for gaseous hydrogen in the atmosphere.
The Chaser was right, H is the chemical formula for metallic hydrogen.
The Contestants were almost right: Chemists don't write H₁ they just write H.

There is a moral to this story.
Be careful when writing questions. The question should not be ambiguous unless you are prepared to accept multiple different answers that are correct.
Be even more careful when answering test and exam questions. If you need to make assumptions to answer the question you MUST state what those assumptions are when you write your answer.

Reference:

1. Ranga P. Dias, Isaac F. Silvera. Observation of the Wigner-Huntington Transition to Metallic Hydrogen. Science, 2017 DOI: 10.1126/science.aal1579

Tutorials Relevant to this Post

Periodic Table of the Elements
Elements and Compounds
Metals and Nonmetals
Molecular Formula

Naming Covalent Compounds
Empirical Formula and Molecular Formula
Trends in Group 1 Elements
Metallic Bonding

Suggested Study Questions

1. Use the Periodic Table of the Elements to find the chemical symbol for each of the following atoms:
• hydrogen
• helium
• carbon
• nitrogen
• oxygen
• chlorine
2. Write a molecular formula for each of the following diatomic gas molecules:
• hydrogen
• nitrogen
• oxygen
• chlorine
3. Give the number of atoms of each element present in the molecular formulae below:
• H₂O
• H₂O₂
• CO
• CO₂
• NH₃
• NO
• NO₂
• N₂O₂
4. Let M represent an atom of an element. Circle the elements below for which the molecular formula of the element at room temperature and pressure could be represented by M
• helium
• sodium
• oxygen
• iron
• gold
• neon
• chlorine
• nitrogen
• hydrogen
5. For the description of each molecule below, write the molecular formula
• one carbon atom and four hydrogen atoms
• one nitrogen atom and three chlorine atoms
• two nitrogen atoms and one oxygen atom
• one nitrogen atom and five oxygen atoms
• two chlorine atoms and two oxygen atoms
• one carbon atom, one hydrogen atom and three chlorine atoms
6. Given the name of each molecule below, write the molecular formula:
• hydrogen chloride
• carbon monoxide
• carbon dioxide
• sulfur dioxide
• sulfur trioxide
• sulfur dichloride
7. Consider the list of compounds with a possible molecular formulae below. Circle the incorrect formulae and justify your answer:
• water, 2HO
• carbon monoxide, C₁O₁
• hydrogen peroxide, H2O₂
• sulfur trioxide: SO₂
• ammonia, NH3
• hydrogen sulfide, H₂S
• carbon dioxide, C₂O
• sulfur dichloride, S₁Cl₂
8. From the list below, circle the elements that belong to Group 1 of the Periodic Table of the Elements:
• sodium
• helium
• oxygen
• lithium
• chlorine
• nitrogen
• carbon
• potassium
• calcium
9. Draw a table with the headings "metal" and "nonmetal". Place each of the following elements in the correct column:
• hydrogen
• helium
• calcium
• carbon
• nitrogen 
• potassium
• oxygen
• chlorine
• sodium
10. From the list below, circle the elements that would exist at room temperature and pressure as an array of "atoms" help together by delocalised electrons:
• hydrogen
• carbon
• sodium
• lithium
• nitrogen
• chlorine
• iron
• gold
• oxygen

Titanium Gold Alloy

Titanium is the metal used to replace hip and knee joints because it is strong, resistant to wear, and, is nontoxic.

Before titanium was used to replace hips and knees, stainless steel was used.
The density of stainless steel used to make replacement hips and knees is about 7.8 g cm³. The density of titanium metal is 4.506 g cm³, about half the density of stainless steel. This means that a replacement joint made out of titanium will weigh less than the same replacement joint made out of stainless steel.
Titanium is also strong. The strength of the material used to replace hip and knee joints is important because you do not want your new joint to bend or break or under strain.

Titanium has a melting point of 1670°C and a boiling point of 3287°C, which means it remains solid over the range of temperatures humans are exposed to. This is important because you want your new hip or knee replacement to remain a solid!
Naturally occurring titanium is made up of a number of isotopes, all of which are stable so they do not undergo nuclear decay. This is important because it means that there is no loss of titanium mass due to radioactive decay, and there is no fear of damage to cells from the emission of radiation.

isotope	atomic mass	abundance
46Ti	45.953	8.25
47Ti	46.952	7.44
48Ti	47.948	73.72
49Ti	48.948	5.41
50Ti	49.945	5.18

Titanium metal will react with water, halogens and dilute hydrochloric acid, but only if the temperature is elevated well above body temperature. Similarly, titanium metal will react with oxygen in a combustion reaction at elevated temperatures. Titanium metal does not appear to react with bases at all. Therefore, titanium is unlikely to react with substances found in the human body.

Researchers at Rice University have found that alloying titanium with gold can produce an even better material to use for replacement hips and knees. Mixing titanium and gold in the ratio of 3:1 at high temperature produces an alloy that is 3 times harder than steel and 4 times harder than the pure titanium commonly in use for hip and knee replacements. The atoms of titanium and gold in this alloy are packed in a cubic arrangement, an arrangement that is usually associated hardness. The structure of this alloy is shown below:

This titanium gold alloy has been found to be even more biocompatible that pure titanium.
The researchers intend to undertake further studies to investigate whether using chemical dopants might improve the alloy's hardness even further.

Reference:
Rice University. "Titanium and gold equals new gold standard for artificial joints: Titanium-gold alloy that is 4 times harder than most steels." ScienceDaily. ScienceDaily, 20 July 2016. 

Further Reading
Metals and Non-metals 
Density
Isotopes
Relative Atomic Mass
Alloys

Suggested Study Questions

1. Titanium and gold are both metallic metallic elements.
   • What are the physical properties common to most metallic elements?
   • What are the chemical properties common to most metallic elements?
2. Draw up a table of the physical properties of titanium.
3. A typical knee replacement made out of titanium has a mass of 560 g.
   • Calculate the volume of the titanium knee replacement.
   • Calculate the mass of the same knee replacement if it were made out of stainless steel
4. Define the term isotope.
5. Determine the number of protons in the nucleus of an atom of each of the isotopes of titanium listed in the article above.
6. Determine the number of neutrons in the nucleus of an atom of each of the isotopes of titanium lists in the article above.
7. Which is the most abundant isotope of titanium? Explain your answer.
8. Use the data in the article above to calculate the relative atomic mass of naturally occurring titanium.
9. Given the atomic radius of titanium is  176 pm (1.76 x 10^-10 m) and the atomic radius of gold is 174 pm (1.74 x 10^-10 m), do you think the alloy of titanium and gold discussed in the article above is an interstitial alloy or a substitutional alloy? Explain your answer.
10. Consider the structure of the titanium gold alloy shown in the diagram in the article above.
    • The blue balls represent which atoms of which element?
    • The red balls represent which atoms of which element?

Alloys

What is an alloy?
What kinds of alloys are there?
Are steel, brass and bronze alloys?
How do the properties of an alloy differ from the properties of the elements making up the alloy?

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Queensland Nickel

In January 2016, Queensland Nickel went into voluntary administration, that is, the company was having difficulty meeting its financial obligations. The story's big news in Australia because Queensland Nickel is 100% owned by one of Australia's most colourful characters, Clive Palmer. Palmer is reputed to be worth about $1 billion and has business interests in minerals and property, including the Palmer Coolum Resort which houses animatronic dinosaurs on its golf course which has been rather controversial. Palmer has been involved in politics since the 1970s firstly as a member of the National Party, then of the Liberal-National Party, then in 2013 he formed his own political party, the Palmer United Party or PUP. And yes, Australians did actually vote PUPs into parliament, including Palmer himself who won the seat of Fairfax  (located in Queensland on the Sunshine Coast, just north of Brisbane, created in 1984 and named after the founder of the Country Women's Association, Ruth Fairfax). But enough of the Australian political history lesson, lets get back to the Queensland Nickel problem.

Nickel is an important metal in our society. More than 80% of the nickel produced worldwide goes into alloys. When alloyed with other metals, nickel imparts toughness, strength and resistance to corrosion as well as various magnetic, electrical and heat resistant properties.  About 65% of all nickel produced is consumed making stainless steel which is used to make cars as well as many other consumer and commercial products, including the kitchen sink!

The worlds largest producers of nickel are the Philippines, Indonesia, Russia, Canada and Australia.

Australia exports about $4 billion of nickel per year, making it an important export commodity. Australia has about 17 million tonnes of nickel reserves. Western Australia has about 96% of these reserves, Queensland about 3.8% and Tasmania about 0.2%. At the current rate of production, these reserves should last about 70 years.

In 1974, nickel mining began at Greenvale, 220 km northwest of Townsville. This nickel ore was transported by train to the Palmer owned refinery at Yabulu,  about 25 km north of Townsville. The Greenvale mine closed in 1992, however, commencing in 1986, nickel ore was shipped from New Caledonia, the Philippines and Indonesia to Townsville then transported by rail to the refinery. The refinery produces about 32,000 tonnes of nickel and 19,000 tonnes of cobalt per year.

The Yabulu plant carries out three process:

1. ore processing
2. mixed nickel-cobalt hydroxide processing
3. nickel and cobalt refining

Nickel ore contains nickel oxide, NiO. Ore processing involves blending, drying, and milling to fine powders.
The fine ore powder is then mixed with fuel oil reductant (C) and reduction roasted at  750°C under reducing conditions achieved by the partial combustion of fuel oil to carbon monoxide and the addition of hydrogen gas. We can represent the reduction of NiO by C as:
                750°C 
NiO + C  --->    Ni + CO

 The reduced ore, containing nickel and cobalt, is cooled and then leached in aqueous ammonium carbonate liquor at atmospheric pressure to selectively dissolve nickel and cobalt. This product liquor contains about 12 g L^-1 Ni and 0.6 g L^-1 Co, while the residual solids in the tailings contain carbonates of manganese and magnesium. The solution containing dissolved nickel and cobalt is separated from the solids and the excess ammonia removed. Patented ammoniacal extraction technology selectively extracts nickel which is then precipitated as basic nickel carbonate,  Ni₄CO₃(OH)₆(H₂O)₄

4 Ni²⁺ + CO₃²⁻ + 6 OH⁻ + 4 H₂O --->  Ni₄CO₃(OH)₆(H₂O)₄

This basic nickel carbonate is dewatered and the product can then be calcined in a rotary kiln under reducing conditions to produce nickel. Calcination drives off carbon dioxide and water to produce nickel calcine, approximately 60% nickel and 40% nickel oxide. After further reduction of nickel calcine using hydrogen, a metal is produced that is 99% nickel:
NiO + H₂  --->  Ni + H₂O
The Palmer-owned Queensland Nickel refinery is still operational, and there is no shortage of nickel ore to refine, so why is the business in danger of closing? 
According to Palmer, the financial difficulties Queensland Nickel find itself in result from a fall in nickel prices  and the Queensland Government's refusal to guarantee a $35 million loan. Certainly nickel prices have been in a general decline, In 2007, the price of nickel peaked at about $50,000 per tonne, in 2008 the price of nickel was about $20,000 per tonne, now it is worth less than half that much, probably because the supply of nickel is simply greater than demand for it. So, why is this story getting so much media attention? Is it because 237 workers at the refinery were sacked? Maybe, but the biggest issue in the media surrounds the purported donations made by the Palmer-owned Queensland Nickel to the Palmer-founded and led political party, PUP, to the tune of $15.2 million donated in 2013-14 financial year and another $5.9 million in 2014-15, which could probably have paid 237 workers for quite a few more months.

References:
http://www.abc.net.au/news/2016-01-16/qld-nickel-donated-nearly-$290k-just-2-weeks-before-sackings/7093096
http://www.smh.com.au/federal-politics/political-news/clive-palmers-political-career-on-the-brink-after-business-meltdown-20160118-gm8a0q.html
http://www.smh.com.au/business/mining-and-resources/clive-palmers-queensland-nickel-in-voluntary-administration-20160117-gm7x8r.html

Further Reading:
Metal Extraction Concepts: http://www.ausetute.com.au/metalextract.html
Carbon Reduction Method: http://www.ausetute.com.au/creduction.html
Redox Concepts: http://www.ausetute.com.au/redox.html
Oxidation States (Numbers): http://www.ausetute.com.au/oxistate.html
Percentage Composition: http://www.ausetute.com.au/percentc.html

Suggested Study Questions:

1. What is the oxidation state (oxidation number) of nickel in each of the following:
   • Ni
   • NiO
   • Ni₄CO₃(OH)₆(H₂O)₄


2. In the reaction:      NiO + C  --->   Ni + CO
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
3. Nickel oxide, NiO, can also react with hydrogen gas in a similar reaction to the one above in order to produce solid nickel, Ni, and water.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
4. Nickel oxide, NiO, can also react with carbon monoxide gas in a similar reaction to the one above in order to produce solid nickel, Ni, and carbon dioxide.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
5. The carbon reduction method can also be used to extract zinc metal from zinc oxide.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
6. Name one other metal that could be extracted from its oxide using the carbon reduction method and explain why this method could be used for this metal.
7. Name a metal that cannot be extracted from its oxide using the carbon reduction method and explain why this method would not work.
8. Native nickel, that is, nickel found as the element and not in compounds, is rarely found in nature on Earth. Explain why.
9. When native nickel is found on Earth, it occurs as an alloy with iron inside large meteorites. Explain why elemental nickel can be found inside these meteorites that landed on Earth.
10. Calcination is the process of heating a compound to drive off carbon dioxide. Nickel(II) carbonate can be calcined to produce nickel(II) oxide. Write a balanced chemical equation for this reaction.
11. The most common application of  calcination is to convert calcium carbonate in limestone into calcium oxide (called lime) in the production of cement. Write a balanced chemical equation for the calcination of calcium carbonate.
12. Assume a nickel ore is composed of 2% NiO, what mass of ore must be processed annually to produce 32,000 tonnes of nickel metal?
13. In 2014 the price of nickel was an average of about $16,000 per tonne, while in 2015 its price had fallen to about $10,000 per tonne. Assuming Queensland Nickel maintained a steady production rate of 32,000 tonnes per year, what was the change in Queensland Nickel's revenue from 2014 to 2015.
14. What do you think contributed most to the financial difficulties of Queensland Nickel, falling nickel prices or millions of dollars in political donations? Justify your answer.

Essential Elements

Most of the mass of the human body is made up of just 6 elements:

• 65% oxygen
• 18.5% carbon
• 9.5% hydrogen
• 3.2% nitrogen
• 1.5% calcium
• 1% phosphorus

Carbon and hydrogen are the building blocks making up organic (carbon) molecules, and so, since the human body is just an incredibly complicated organic chemical factory, it is no surprise that carbon and hydrogen make up such a huge amount of the mass of a human body. Oxygen is present in most of the biochemicals making up your body, while nitrogen is an essential component of proteins. Why is there so much phosphorus? Phosphorus and oxygen combine to make up the glue that holds your DNA together, no phosphorus, no DNA, no you! And calcium is ofcourse present in bones and teeth.
Then there are minor amounts of other elements such as potassium, sulfur, sodium, chlorine and magnesium which make up less than 1% of the remaining mass of the human body.

Some elements, like iron, are absolutely essential in order for the human body to survive, but are present in extremely minute amounts, for iron this is about 0.006%

H																		He
Li	Be												B	C	N	O	F	Ne
Na	Mg												Al	Si	P	S	Cl	Ar
K	Ca		Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
Rb	Sr		Y	Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
Cs	Ba	*	Lu	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
Fr	Ra	**	Lr	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Uut	Fl	Uup	Lv	Uus	Uuo
		*	La	Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb
		**	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No

Vanderbilt University Scientists have just found out that bromine is also essential.It appears that bromine is important to an enzyme that is used to make a particular type of sulfur-nitrogen bond within the collagen IV structure used to make the scaffold for cells.

Reference:
A. Scott McCall, Christopher F. Cummings, Gautam Bhave, Roberto Vanacore, Andrea Page-McCaw, Billy G. Hudson. Bromine Is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture. Cell, 2014; 157 (6): 1380 DOI: 10.1016/j.cell.2014.05.009

Further Reading
Periodic Table
Metals and Non-metals

Percentage Composition
Mass-Mole Calculations 

Suggested Study Questions:

1.  Give the chemical symbol for each of the following elements:
   • oxygen
   • carbon
   • hydrogen
   • nitrogen
2. Give the name for each of the following elements:
   • Fe
   • Ca
   • P
   • K
   • Mg
3. Give the atomic number for each of the following elements
   • sulfur
   • sodium
   • iodine
   • Cl
   • F
   • Br
4. Make a table of the metals and non-metals named in the article above
5. Chris the Chemist has a mass of 90 kg. Calculate the mass, in kilograms, of each of the following elements in Chris' body
   • carbon
   • hydrogen
   • oxygen
   • nitrogen
6. Calculate the mass of iron in Chris' body in
   • kilograms
   • grams
   • milligrams
   • micrograms
7. Calculate the moles of each of the following elements found in Chris' body
   • carbon
   • hydrogen
   • oxygen
   • nitrogen
8. Do you think Scientists will one day claim that lead is an element essential for human life? Explain your answer.

What's $1 Really Worth?

Have you ever wondered what the value of the metal used to make a coin is?
The Australian $1 coin has a mass of 9 grams and is composed of:

• 92% copper
• 6% aluminium
• 2% nickel

 If we convert each percentage to a mass, then the Australian $1 coin is composed of:

• 92/100 x 9 = 8.28 g of copper
• 6/100 x 9 = 0.54 g of aluminium
• 2/100 x 9 = 0.18 g of nickel

The following are the approximate costs per tonne for each metal:

• copper: $ 7000 per tonne
• aluminium: $ 1750 per tonne
• nickel: $ 19 000 per tonne

Now we convert the cost of each metal per tonne to a cost per gram:

• copper: $7000/1000 = $7 per kg = 7/1000 = $0.007 per gram = 0.7 cents per gram
• aluminium: $1750/1000 = $1.75 per kg = 1.75/1000 = $0.00175 per gram = 0.175 cents per gram
• nickel: $19000/1000 = $19 per kg = 19/1000 = $0.019 per gram = 1.9 cents per gram

Then calculate the value of each of metal used to make an Australian $1 coin:

• copper: 8.28 g x 0.7 cents per gram = 5.796 cents
• aluminium: 0.54 g x 0.175 cents per gram = 0.0945 cents
• nickel: 0.18 g x 1.9 cents per gram = 0.342 cents

The value of an Australian $1 coin is
5.796 cents + 0.0945 cents + 0.342 cents = 6.2325 cents!

Further Reading:
Percentage Composition Calculations
Mass Conversions

Calculate the value of each of the following coins:

1. Australian $2 coin has a mass of 6.60 g and is composed of  92% copper, 6% aluminium, 2% nickel
2. Australian 50 cent coin has a mass of 15.55 grams and is composed of 75% copper, 25% nickel
3. Australian 20 cent coin has a mass of 11.31 grams and is composed of 75% copper, 25% nickel
4. Australian 10 cent coin has a mass of 5.66 grams and is composed of 75% copper, 25% nickel
5. Australian 5 cent coin has a mass of 2.83 grams and is composed of 75% copper, 25% nickel
6. An American nickel (5 cent coin) has a mass of 5.00 grams and is composed of 75% copper, 25% nickel
7. An American dime (10 cent coin) has a mass of 2.268 grams and is composed of 91.67% copper, 8.33% nickel
8. An American quarter (25 cent coin) has a mass of 5.67 grams and is composed of 91.67% copper, 8.33% nickel

Ancient Elements

Only about a dozen elements were known to the people living in ancient civilizations.

• Copper beads dating from about 6000 B.C. have been found in Turkey.

• A lead statuette found in an Egyptian temple dates from around 3800 B.C. and golden artefacts have also been found in ancient Egyptian tombs.

• Silver was used by the ancient Greeks and Romans to prevent infection, and was used as an early form of currency.

• There is evidence of the systematic production of iron in Turkey around 2000 B.C. for use in tools and weapons.

• Carbon, in the form of diamonds, was also known in the Ancient world, but, carbon in the form of charcoal was far more important to these early people because it could be used in the production of copper, tin, and therefore bronze (an alloy of copper and tin).

• Sulfur was also known to the Ancient Egyptians and Greeks, who used it as a medicine.

• The ancient Chinese, Indians and Egyptians also knew about mercury, using it in ointments and cosmetics.

• Before 1000 B.C., Indians were extracting zinc from its ores. Ornaments containing 80% or more of zinc have been found.

• During the Bronze Age (an earlier period than the Iron Age), arsenic was included in bronze to make the alloy harder. Ancient people understood that they could produce arsenic by heating certain substances (which we would now call arsenic sulfides and oxides).

• Antimony was used in cosmetics in the Ancient world, notably by the Egyptians who used it around their eyes (known as kohl).

• Chromium has been found in ancient Chinese artifacts. The weapons the Chinese Terracotta Army carry are coated in chromium oxide and date from around the 3rd century B.C.

In fact, these were really the only elements known  until the 17th century A.D.
Today we know of over a 100 elements.
Chemistry has come a long way in the last few hundred years!

Further Reading:
History of the Elements
Metal Extraction Concepts
Periodic Table
Metals and Non-metals
Pure Substances and Mixtures

Suggested Study Questions:

1.  Find each of the elements mentioned above on the Periodic Table.
2. Draw up a table of the name and chemical symbol for each of the elements mentioned above.
3. Draw up a table classifying each of these elements as metals, non-metals or semi-metals (metalloids).
4. Name a mixture mentioned in the article above.
5. Name a compound mentioned in the article above.
6. There are only 3 metallic elements that are not a "silvery" colour. One of these is cesium (or caesium), but if the sample of cesium is very pure it loses its golden colour. Name the other two non-silvery metallic elements.
7. Explain why you often find weapons like swords made of iron, but you never find functional weapons made of gold.
8. Explain why you find ornamental weapons made out of gold, but rarely out of zinc.
9. Ancient people could have produced mercury by heating cinnabar (mercury(II) sulfide). The cinnabar decomposes, producing liquid mercury and sulfur. Write a word equation for the decomposition of cinnabar.

Phlogiston Theory

Before the modern chemical ideas of atoms and elements, phlogiston theory was a widely held belief.
According to phlogiston theory, matter consisted of three essential essences:

• sulfur (terra pinguis - the essence of inflammability, which was to become known as phlogiston)
• mercury (terra mercurialis - the essence of fluidity)
• salt (terra lapida - the essence of fixity and inertness)

 Phlogiston theory was an early attempt to to try to explain what happened when things were burnt or combusted. In phlogiston theory, substances were made up of a "calx" (or residue) combined with phlogiston (the essence of inflammability). When a substance was burnt (combusted), phlogiston was released, and the residue (calx) was left behind. Even the rusting of iron could be explained using phlogiston theory, because the "iron" would lose its phlogiston during the rusting process and leave behind the "calx" or residue. One of the problems with the phlogiston theory is that metals should lose mass when they burn, owing to the loss of phlogiston.

In the 18th century, Antoine-Laurent de Lavoisier, the man who is considered to be the father of modern of modern chemistry, conducted a series of combustion experiments. In these experiments he carefully weighed the substances to be combusted as well as the products of combustion, and found that the weight of the products of combustion was greater than the weight of the substance before combustion. He also demonstrated that when a substance corrodes in a sealed container, the gain in weight of the substance is equal to the loss in weight of the air in the container.
This was the beginning of the downfall of the phlogiston theory, but it was the beginning of the modern chemistry when Lavoisier generalized that if the weights of all substances involved in a chemical reaction are considered then there is no overall loss or gain in weight.

Further Reading:
http://www.ausetute.com.au/elemhist.html
http://www.ausetute.com.au/elements.html
http://www.ausetute.com.au/atomichist.html
http://www.ausetute.com.au/wriiform.html
http://www.ausetute.com.au/namiform.html
http://www.ausetute.com.au/namcform.html
http://www.ausetute.com.au/balcheme.html

Suggested Study Questions

1. Lavoisier burnt sulfur. When sulfur burns in air, it reacts with oxygen to form sulfur dioxide. Write a word equation for this reaction.
2. Write the chemical formula for each of the following:
   • sulfur
   • oxygen gas
   • sulfur dioxide gas
3. Write a balanced chemical equation for the combustion of sulfur to produce sulfur dioxide gas.
4. If Lavoisier had weighed out 32 grams of sulfur and then burnt it in air, the sulfur dioxide he collected would have a mass of 64 grams. What mass of oxygen would have been reacted with the sulfur? 
5. Explain why a substance such as sulfur appears to gain mass when it is combusted.
6. When wood is burnt, the mass of the ashes left behind is actually less than the mass of wood you started with. How do you explain this loss of mass?
7. Magnesium is a metal that combusts readily in oxygen gas to form magnesium oxide.
   • Write a word equation for the combustion of magnesium to form magnesium oxide,
   • Write a balanced chemical equation for this reaction.
8. If 20.16 grams of magnesium oxide is produced as a result of the combustion of 12.16 grams of magnesium, how much oxygen gas was consumed during the reaction?
9. Imagine you are living in the 18th century and that you are a firm believer in the phlogiston theory. How would you explain to Lavoisier how metals gain mass when they burn?

Gallium Practical Jokes

If you ask a Chemist what their favourite metal is, the chances are they will answer gallium.

Historically, gallium is significant because it was one of the elements that Dmitri  Mendeleev predicted the properties of, before the element had even been discovered! Mendeleev called the element ekkaaluminium.

Gallium has gained commercial value because gallium compounds such as gallium arsenide, GaAs, are important semiconductors in the electronics industry.

But the reason many Chemists like gallium is because of its interesting physical properties.
Gallium is a silvery metal with a metallic lustre that looks a lot like silver. Unlike silver however, gallium is not found as the element in nature. Gallium compounds occur in minute quantities in bauxite (an aluminium ore) and sphalerite (a zinc ore) and can be extracted from these ores by smelting.
The melting point of gallium is about 29.8^oC and its boiling point is about 2204^oC. This means that at temperatures between 29.8^oC and 2204^oC gallium is a liquid. Or put another way, if you have some gallium in a test tube on a hot summer's day in Sydney, or Miami, or anywhere where the temperature gets above 30^oC, what you will see is a puddle of molten metal, but if you take the molten gallium back into an air-conditioned room where the temperature is likely to be less than 25^oC, the gallium will freeze again.
And this is the basis of the disappearing spoon trick as shown in the video.

At temperatures below its melting point, gallium is a solid and can be fashioned into a spoon shape.  Being a silvery, metallic metal, it looks just like a silver teaspoon. However, if you were to stir your cup of hot tea or hot coffee with the gallium spoon, the spoon will melt because the temperature of the tea or coffee will be above the melting point of the gallium.



Further Reading
History of the Periodic Table
Periodic Table of the Elements
Metals and Non-metals
Chemical and Physical Changes
Writing Ionic Formula
Naming Ionic Compounds
Temperature Conversions
Latent Heat

Suggested Study Questions

1. Use the Periodic Table to find the following for gallium:
   • symbol
   • atomic number
   • atomic mass
2. With reference to the Periodic Table explain why Mendeleev would have named the unknown element, located where gallium is now known to be, ekkaaluminium.
3. Gallium often occurs in compounds in the +3 oxidation state, or as an ion in salts with a charge of 3+. Give the most likely formula for each of the following:
   • gallium chloride
   • gallium oxide
   • gallium hydroxide
4. Give the most likely name for each of the following:
   • GaH₃
   • Ga(NO₃)₃
   • Ga₂(CO₃)₃
5. Does the video show a chemical or a physical process? Explain your answer.
6. Sketch a temperature vs time curve to describe the melting of gallium.
7. Convert the melting point and boiling point of gallium from centigrade to kelvin.
8. Mercury has a melting point of about 234K and a boiling point of around 630K. Convert these temperatures to ^oC
9. Explain why mercury is a liquid at room temperature and pressure.
10. Could you freeze mercury by walking into an air-conditioned room like you can gallium? Explain your answer.

New Metallurgy Resources

AUS-e-TUTE has just added new tutorials, games, tests, and drills to its metallurgy section.
The new sections include:
Metal + Water Reactions
Metal + Non-oxidizing Acid Reactions
Metal + Oxygen Gas Reactions
Activity Series (metals)

Olympic Medal Metals

Metallic medals have been awarded to 1^st, 2^nd and 3^rd place Olympic athletes since the 1900 Paris Olympic Games. The medals awarded at the 2012 London Olympic Games are 7mm thick, 85 mm in diameter, and, weigh 400g.
While we happily refer to these olympic medals as gold, silver and bronze, is this chemically accurate?

"Bronze medals" are often made of bronze, an alloy of copper and tin.
At the 2012 London Olympic Games, the bronze medals are made up of a mixture of 97% copper, 2.5% zinc and 0.5% tin. This composition is actually much closer to the composition of brass which is the term used to refer to an alloy of copper and zinc.

"Silver medals" contain at least 92.5% silver. The silver medals awarded in the 2012 Olympic Games were composed of 92.5% silver and 7.5% copper.

"Gold medals" must also contain at least 92.5% silver, but they are plated with at least 6g of gold so they look like "gold" medals. The 2012 Olympic gold medals are made up of 92.5% silver, 6.16% copper and 1.34% gold.

Reference

www.olympic.org/Assets/OSC%20Section/pdf/QR_1E.pdf

Further Reading
Periodic Table
Percentage Composition
Mass-mole Calculations
Moles-Number of Particle Calculations
Density Calculations

Suggested Study Questions

1. Give the chemical symbol for each of the following elements:
   • gold
   • silver
   • copper
   • tin
   • zinc
2. Explain why chemists refer to bronze and brass as alloys.
3. Calculate the mass of each element present in the bronze olympic medals awarded in 2012.
4. Calculate the mole of each element present.
5. For the 2012 Olympic gold medal, calculate the mass of silver present.
6. Calculate the number of silver atoms present in a 2012 olympic gold medal.
7. Calculate the mass of gold present in a 2012 olympic gold medal.
8. Calculate the volume of an olympic medal and use this to calculate the density of an olympic medal.
9. Calculate the surface area of a 2012 Olympic gold medal.
10. Assuming the 2012 gold medal is coated evenly with gold, what thickness is the layer of gold?

Sunken Silver

In 1941, the British cargo ship SS Gairsoppa was carrying 7,000 tonnes of cargo from Calcutta. The cargo included pig iron, tea and about 200 tonnes of silver. A German U-boat torpedo sunk the SS Gairsoppa as it made its way to Ireland in stormy weather. While only one person out of the 85 crew members on board survived the attack, it is believed its cargo of silver is still at the bottom of the ocean.

Silver is unique because it has the highest electrical and thermal conductivity of any known element. It is a soft metal, just a little harder than gold, and is extremely ductile and malleable meaning it can be bent or beaten into almost any shape.
There were many uses for silver during World War II :

• many electrical connectors and switches were silver plated
• silver bus bars were needed for the new aluminum plants (aluminium aircraft)
• silver replaced large amounts of tin in solder
• silver was used in the reflectors in lights

There are a number of silver alloys:

• Fine silver contains 99.9% by mass silver
• Britannia silver contains 95.84% by mass silver with copper making up the remaining mass
  
• Sterling silver contains 92.5% by mass silver and 7.5% by mass copper.
• Argentium sterling silver is a modern alloy containing 92.5% silver and 7.5% by mass of copper and germanium
• Electrum is a natually occurring alloy of gold and silver. The % by mass of gold can be within the range of 70-90%.

And, silver is present in most coloured carat gold alloys:

• 9 carat gold contains 62.5% silver and 37.5% gold
• 22 carat gold contains 91.7% gold with the remaining mass made up of silver and/or copper
  

Silver is stable in pure air and water, but tarnishes when exposed to air or water containing ozone or hydrogen sulfide. In the presence of oxygen gas and hydrogen sulfide gas, elemental silver forms the dark-coloured silver (I) sulfide and water.

Reference
Shipwreck of SS Gairsoppa reveals £150m silver haul
BBC News Online
http://www.bbc.co.uk/news/uk-15061868

Further Reading
Properties of Metals and Non-metals
Percent by Mass
Writing Ionic Formula
Balancing Chemical Equations

Suggested Study Questions

1. For the element silver, give the
   • chemical symbol
   • atomic number (Z)
   • atomic mass
     
2. For each of the uses given for silver in the article above, explain which physical and/or chemical properties of silver make it ideal for that use.
3. Using the composition of the various silver alloys provided in the article above, place the alloys in order of increasing mass of silver present in a 1kg sample.
4. Using the information contained in the article above, describe the relationship between the mass of gold in a sample and the use of the term carat.
5. Place the following terms in order of decreasing mass of gold: 9 carat gold, 18 carat gold, 22 carat gold and 24 carat gold.
6. Write a word equation to describe the process of tarnishing in air that contains some hydrogen sulfide.
7. Write a balanced chemical equation for the tarnishing of silver in air that contains some hydrogen sulfide.
8. It is thought that the silver being carried by the SS Gairsoppa contained some gold. Which alloy of silver could this be? Explain your answer.
9. The SS Gairsoppa is resting 4,700m below the ocean's surface. Do you expect the silver to be tarnished? Explain your answer.
   

Rhodium

Rhodium, symbol Rh, is the rarest of all non-radioactive metals on Earth, and therefore an expensive metal. On the 22nd July 2011, 1 gram of rhodium cost $(AUD)38 compared to 1 gram of gold which cost $(AUD)31 or 1g of silver for only 78 cents !
Rhodium is a transition metal with a density of 12.41 gcm^-3 and is found in nature as the free metal, or alloyed with similar metals such as platinum or nickel, but not as a chemical compound.
Naturally occurring rhodium is composed of only one isotope, rhodium-103.
Only about 3 tonnes of rhodium are produced in the world each year, and most of this is used for catalyzing chemical reactions.
Approximately 80% of the rhodium produced is used as a reduction catalyst in the three-way catalytic converters of cars.
In a three-way catalytic converter three processes occur simultaneously:

1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NO_x → xO₂ + N₂
2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O₂ → 2CO₂
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water

Other uses of rhodium include :

• plating white gold to make it appear more silvery (white gold is actually an alloy of gold with atleast one other metal such as nickel, manganese, palladium)
• plating sterling silver to make it appear more silvery (sterling silver is an alloy of silver containing 92.5% by mass silver and 7.5% by mass of other metals such as copper)

Queen's University chemists have just discovered that rhodium that is modified using carbon, nitrogen or hydrogen-based complexes changes colour to yellow in the presence of nitrogen, deep blue in the presence of oxygen, and brown in the presence of carbon monoxide. Modified metals, such as modified rhodium, that change colour in the presence of particular gases could warn consumers if packaged food has been exposed to air or if there's a carbon monoxide leak at home. This finding could potentially influence the production of both industrial and commercial air quality sensors.

Reference
Queen's University (2011, July 21). Modified metals change color in the presence of particular gases. ScienceDaily. Retrieved July 23, 2011, from http://www.sciencedaily.com­ /releases/2011/07/110721131159.htm

Further Reading
Periodic Table
Definitions of a Mole
Mass-Mole Calculations
Density
Isotopes
Relative Atomic Mass
Metals & Non-metals
Percentage Composition

Study Questions

1. Locate rhodium in the Periodic Table and give its
   • atomic number
   • relative atomic mass
2. Using the prices per gram of metal given in the story above, calculate
   • the price of the 3 tonnes of rhodium produced in the world each year
     
   • the price of 1 mole of rhodium
   • the price of 10 cubic centimeters of rhodium
   • the mass of $57,000 worth of rhodium
   • the volume of $57,000 worth of rhodium
3. Naturally occurring rhodium has only 1 isotope, rhodium-103. For this isotope give:
   • the number of protons in the nucleus of a rhodium atom
   • the number of neutrons in the nucleus of a rhodium atom
   • the mass number of this isotope of rhodium
   • the atomic number for this isotope of rhodium
4. If naturally occurring rhodium only has 1 isotope why is its relative atomic mass 102.9?
5. List the physical properties you would expect rhodium to have based on its position within the Periodic Table.
6. Why would coating white gold in rhodium make it appear more silvery?
7. A 25 kg sample of sterling silver contains only silver and copper.
   • What mass of silver is present in the sample?
   • What mass of copper is present in the sample?
8. A sample of white gold is found to contain only 1.39 g gold and 0.09g of nickel. Calculate the percent by mass of each element present in the sample.
   
   
   
   
   

Metallic Hydrogen Superconductor

Superconductors are materials that permit electricity to travel freely, without resistance, so they could dramatically improve the efficiency of power transmission technologies. Metallic hydrogen should be just such a superconductor.

Liquid metallic hydrogen is thought to exist in the high-gravity interiors of Jupiter and Saturn.
Scientists have predicted that electricity would flow, uninhibited, through a material made by compressing hydrogen into a metal. But so far, on Earth, researchers have been unable to use such compression techniques to squeeze hydrogen under high enough pressures to convert it into a metal. University at Buffalo chemists have now proposed an alternative solution for metallizing hydrogen by adding sodium to hydrogen which they think might make it possible to convert the compound into a superconducting metal under significantly lower pressures.

NaH₉, which does not occur naturally on Earth but is expected to be a stable compound, is predicted to become metallic at an experimentally achievable pressure of about 250 gigapascals, about 2.5 million times Earth's standard atmospheric pressure, but less than the pressure at Earth's core which is about 3.5 million atmospheres.

Reference
University at Buffalo (2011, June 13). Under pressure, sodium, hydrogen could undergo a metamorphosis, emerging as superconductor. ScienceDaily. Retrieved June 15, 2011, from http://www.sciencedaily.com­ /releases/2011/06/110613162240.htm

Further Reading
Metals and Non-metals
Kinetic Theory of Gases

Study Questions

1. Draw up a table listing the properties of metals and non-metals.
2. In what ways is elemental hydrogen like a non-metal?
3. In what ways is elemental hydrogen like a metal?
4. Use the Kinetic Theory of Gases to explain what you expect to happen as elemental hydrogen at atmospheric pressure is subjected to increasing pressure.
5. Using the Kinetic Theory of Gases, describe two ways that scientists could, in theory, make solid hydrogen.
6. Using the Kinetic Theory of Gases, explain why hydrogen might exist as a liquid in the interior of the planet Jupiter.
   
7. If 250 gigapascals is about 2.5 million times Earth's standard atmospheric pressure, what does the prefix "giga" stand for?
   
8. Why do you think that chemists suggest adding sodium to hydrogen to create a solid material capable of conducting electricity?
   

Germanium

The element germanium, symbol Ge and atomic number 32, is part of a frequently studied group of elements, Group IVa of the periodic table, which could have applications for next-generation computer architecture. It is currently used in fiber-optic systems, specialized camera and microscope lenses, circuitry, and solar cells. It is a semi-conductor so it is useful in electronics.

In 1869, Dmitri Mendeleev predicted the existence of an element in Germanium's position in his periodic table and called the element eka-silicon. Mendeleev predicted the properties of this undiscovered element based on the properties of the elements around it. In 1886 Clemens Winkler found the element in the mineral argyrodite, named it after his homeland, Germany, and reported its properties. Winkler's observed properties for germanium agreed very well with Mendeleev's predictions for ekasilicon:

Property	Ekasilicon	Germanium
atomic mass	72.64	72.59
density (g/cm3)	5.5	5.35
melting point (°C)	high	947
color	gray	gray
oxide type	dioxide	dioxide
oxide density (g/cm3)	4.7	4.7
oxide activity	weak base	weak base

Germanium can form compounds similar to those formed by carbon and silicon.
Germane, GeH₄, is a compound similar in structure to methane, CH₄.
Polygermanes with general formula Ge_nH_2n+2, where n is 1 to 5, are known.

Germanium is a semiconducting solid at room temperature and pressure. It has been predicted that, under pressure, the element should exhibit superconductivity, meaning that there is no resistance to the flow of an electric current.

Scientists at the Geophysical Laboratory at Carnegie Institution for Science have recently discovered that under pressure of 66 GPa (about 650,000 atmospheres), germanium undergoes a structural change from one type of solid material to another that is metallic, meaning it conducts electricity.

Reference
Xiao-Jia Chen, Chao Zhang, Yue Meng, Rui-Qin Zhang, Hai-Qing Lin, Viktor Struzhkin, Ho-kwang Mao. β-tin→Imma→sh Phase Transitions of Germanium. Physical Review Letters, 2011; 106 (13) DOI: 10.1103/PhysRevLett.106.135502

Further Reading
Periodic Table
History of the Periodic Table
Metals and Non-metals
Naming Carbon Compounds

Study Questions

1. Give the name and symbol for each element present in Group IVa of the Periodic Table.
   
2. Germanium is known to form germanium dioxide. Write the formula for germanium dioxide.
3. Which of the other Group IVa elements form dioxides? Give the name and formula for each of these compounds.
4. Could germanium form any other oxides? Explain your answer.
5. Draw up a table listing the electrical conductivity of each of the Group IVa elements. Explain any trend that you see.
6. Draw a structural formula for germane.
7. Explain why it would be predicted that germanium could form "polygermanes" similar to carbon's alkanes.
8. Predict the formula for the compound(s) formed between germanium and chlorine. Explain each prediction.
   

Lithium for a Longer Life

Lithium is the 25^th most abundant element in the Earth's crust, with approximately 20mg of lithium present in every kilogram of crustal material. It is a soft, silvery-white metal that belongs to Group I (alkali metals). It is so highly reactive that when it is cut in air it will quickly corrode before your eyes. In the presence of water, lithium reacts to form hydrogen gas and lithium hydroxide in aqueous solution. Because it is so reactive, lithium does not occur free in nature, it only appears naturally in compounds.

Lithium-6 and lithium-7 were among the three elements synthesized in the Big Bang according to cosmological theory, the other two elements being hydrogen and helium. Lithium is present in cooler, less massive brown dwarf stars but is destroyed in hotter red dwarf stars, so its presence in the stars' line emission (atomic) spectra can be used to differentiate between these two kinds of stars in the so-called 'lithium test'.

Trace amounts of lithium ions are present in the oceans. The total lithium content of seawater is estimated to be 230 billion tonnes, and is present in concentrations of about 0.2 parts per million.
Lithium is also present in trace amounts in plants and animals. Vertebrates contain lithium in concentrations between 21 and 763 parts per billion.

Lithium salts, such as lithium carbonate, have been to shown to be useful as mood-stabilizing drugs. Therapeutically useful amounts of lithium are between 1.0 and 1.2 millimolar, which is only slightly lower than the toxic amount of 1.5 millimolar.

Scientists at the Friedrich Schiller University Jena have just demonstrated that a regular uptake of lithium could lead to a longer life. The scientists studied the impact of lithium in a concentration that is regularly found in ordinary tap water by analyzing the mortality rate in 18 adjacent Japanese municipalities in relation to the amount of lithium contained in tap water from the respective regions. They found that the mortality rate was considerably lower in those municipalities with more lithium in the drinking water.

Reference
Kim Zarse, Takeshi Terao, Jing Tian, Noboru Iwata, Nobuyoshi Ishii, Michael Ristow. Low-dose lithium uptake promotes longevity in humans and metazoans. European Journal of Nutrition, 2011; DOI: 10.1007/s00394-011-0171-x

Further Reading
Elements and Compounds
Metals and Non-metals
Trends in Group I
Electron Configuration
Naming Ionic Compounds
Writing Ionic Formulae
Parts per Million Concentration
Molarity Concentration
Emission (Atomic) Spectra
Isotopes
Relative Atomic Mass

Study Questions

1. What is the atomic number of lithium?
2. What is the simple electron configuration for an atom of lithium?
3. What is the expected charge on a lithium ion? Explain your answer.
4. Write the formula for each of these compounds:
   
   • lithium hydroxide
   • lithium carbonate
5. Write a balanced chemical equation to represent the reaction between lithium metal and water.
6. For each of the following isotopes of lithium, give the number of protons and the number of neutrons present:
   
   • lithium-6
   • lithium-7
7. Given that the relative atomic mass of lithium is 6.941, and assuming lithium-6 and lithium-7 are the only isotopes of lithium present, calculate the abundance of each isotope.
8. Convert the following to concentrations in molL^-1 (M):
   
   • 0.2ppm
   • 1.2millimolar
   • 1.5millimolar
     
   • 21ppb
   • 763ppb
9. If the total lithium content of seawater is estimated to be 230 billion tonnes, and is present in concentrations of about 0.2 parts per million, what is the mass of seawater present on Earth?
10. In the 'lithium test' for stars, what spectral lines do you expect to see in brown dwarf stars that will not be present in red dwarf stars?