Question

Deduce the number of neutrons from the atomic number (Z) and mass number (A). [3 marks]

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