Solution:
i. Atomic mass number is the sum of protons and neutrons in an atom e.g. chlorine which has 17 protons and 18 neutrons has a mass 35.
ii. Nuclear charge is the sum of proton charges in the nucleus. Na has 11 protons; its nuclear charge is (l).
iii. Valency is the combining power of an atom when it reacts with another to from a bond. Valency of oxygen equal 2 because Q²−
iv. Isotopy is the occurrence of two or more atoms of an element with different numbers of neutrons or atomic mass number. e.g. carbon, oxygen, chlorine. e.t.c.
Carbon has 12 – C and 14- C for Carbon, with the same atomic number of 6
Oxygen has 16 – O and 18 – O for Oxygen, with the same atomic number of 8
