Which of the following pairs of 'number – composition' is correct?
I. Atomic number – number of protons
II. Mass number – Sum of number of neutrons and protons
1
Only I
2
Neither I nor II
3
Both I and II
4
Only II
Which of the following pairs of 'number – composition' is correct?
I. Atomic number – number of protons
II. Mass number – Sum of number of neutrons and protons