How do you tell if an oxide is acidic, basic, amphoteric?
How do you know what sort of bonding and structure an oxide has?
What happens if you add on oxide to some strong acid?
What happens if you add an oxide to some strong base?
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The Periodic Table of the Elements is a truly amazing tool, it contains an incredible amount of information in a very small space.
One of the first skills chemistry students need to master is how to extract all this valuable information about elements from the Periodic Table.
AUS-e-TUTE already has a number of resources to help students develop these skills, but we've just added a new set of resources to help you locate the s block, p block, d block and f block elements.
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After The Jade Rabbit lander touched down on the Moon in
December 2013, the Chinese space agency publicly suggested establishing mining
bases on the Moon.
What could be so valuable that it would warrant the cost of
going to the Moon to mine it then bringing it back to Earth to be used?
Gold? No.
Diamonds? No again.
Rare earth elements!
Why have rare earth elements (REE) become so important?
Find out in this edition of AUS-e-NEWS.
If you haven't received your December 2016 issue of AUS-e-NEWS in your inbox, please email us at
Question: Write the symbol for the element which has the smallest atomic radius Na, Si, Mg, P.
Answer: In general, atomic radius decreases going across a period of the Periodic Table.
Sodium (Na), magnesium (Mg), silicon (Si) and phosphorus (P) all belong to the third period.
In order of increasing atomic number they are: Na (Z=11), Mg (Z=12), Si (Z=14), P(Z=15)
Therefore, in order of decreasing atomic radius they are: Na > Mg > Si > P
So, phosphorus, symbol P, has the smallest atomic radius.
Astatine is the product of the radioactive decay of some heavier elements and is the rarest naturally occurring element on Earth, only a few grams of astatine is estimated be present in the whole of the Earth's crust at any one time. All of astatine's isotopes are short-lived, with astatine-210 having the longest half-life of all its isotopes, 8.1 hours. As a result, astatine was unknown until 1940, when scientists bombarded bismuth-209 with alpha particles and produced astatine.
Even today we don't know very much about astatine, but estimates about its properties have been made based on its position in the Periodic Table, right under iodine in Group 17 (halogens). The first ionization energy of astatine has been estimated to be between 849.11 and 926.29 kJ/mol (8.8 and 9.6 eV).
The ionization energy, the energy required to remove an electron from the valence shell of an atom, is one of the most important properties that influences the chemical behaviour of an element.
In May 2013 an international team of researchers announced that they had measured the first ionization energy of astatine using laser ionization spectroscopy and found it be be 9.31751 eV (899.02 kJ/mol)
Reference: Rothe, S. et al. Measurement of the first ionization potential of astatine by laser ionization spectroscopy. Nat. Commun. 4:1835 doi: 10.1038/ncomms2819 (2013).
How many valence electrons does an atom of astatine have? Explain your answer.
Describe the trend in melting points as you go down astatine's group in the periodic table, then estimate the melting point of astatine.
Describe what you think astatine would look like at room temperature and justify your answer on the basis of trends in the periodic table.
How does astatine-207 differ from astatine-210?
Astatine-211 and 2 neutrons are produced when bismuth-209 is bombarded with alpha particles.Write a nuclear equation for this reaction.
Imagine working in a laboratory. You have been given 100 μg of astatine-210 at 9 am for your experiment. Assuming the half-life of astatine is 8 hours, how much astatine-210 would you have left when you leave the lab at 5 pm?
The half-life of astatine-219 is about 1 minute. If you had 100 μg of astatine-219 at 9 am, how much astatine-219 would you have 5 minutes later at 9:05 am ?
Use the information in the article above to estimate the conversion factor between electronvolts (eV) and kJ/mol.
Why do we not have an accurate measure of how much astatine is found in the Earth's crust?
Suggest a way that scientists can estimate the amount of astatine in existence in the Earth's crust.
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 29.8oC and its boiling point is about 2204oC. This means that at temperatures between 29.8oC and 2204oC 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 30oC, 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 25oC, 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.
Use the Periodic Table to find the following for gallium:
symbol
atomic number
atomic mass
With reference to the Periodic Table explain why Mendeleev would have named the unknown element, located where gallium is now known to be, ekkaaluminium.
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
Give the most likely name for each of the following:
GaH3
Ga(NO3)3
Ga2(CO3)3
Does the video show a chemical or a physical process? Explain your answer.
Sketch a temperature vs time curve to describe the melting of gallium.
Convert the melting point and boiling point of gallium from centigrade to kelvin.
Mercury has a melting point of about 234K and a boiling point of around 630K. Convert these temperatures to oC
Explain why mercury is a liquid at room temperature and pressure.
Could you freeze mercury by walking into an air-conditioned room like you can gallium? Explain your answer.
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 GenH2n+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.
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