This is a headline from the Sydney Morning Herald, Friday 1 st March 2019, " Three hospitalised after chemical spill at Lucas Heights...

What is the mass number of an atom? Why is it called a "mass number"? How many nucleons are in an atom of an element? How many ...

number of protons in an atom = atomic number (Z) of the element ... and.... the periodic table of the elements lists the elements in o...