The table shows the mass numbers and abundances of naturally occuring copper isotopes. 

Mass number Abundance
63 69%
65 31%


What is the relative atomic mass to 1 decimal place? 


An atom of phosphorus has the symbol  

Give the number of protons, neutrons and electrons in this atom of phosphorus: 

A. Number of protons [[15]] 

B. Number of neutrons [[15.97]]

C. Number of electrons [[15]] 


The mass number of an atom is worked out by what?