Question

Deduce the number of neutrons from the atomic number (Z) and mass number (A).

Answer 1

Atomic number (Z) is equal to the number of protons present in the nucleus of an atom. (1 Mark)
Mass number (A) is equal to the sum of the number of protons and neutrons present in the nucleus of an atom. (1 Mark)
If the number of protons in the nucleus = p and neutrons = n.
So, Z = p and A = n+p
A - Z = n. (1 Mark)
So the value of the number of neutrons present in the nucleus of an atom = n = A - Z. (1 Mark)