Question

What is meant by atomic mass number ? Explain how the atomic number and mass number of carbon are 6 and 12 respectively.

Answer 1

Atomic Mass Number : It is the sum of total number of protons and neutrons present in a nucleus. (1 Mark)
Atomic mass number = number of protons + number of neutrons.
Atomic number = number of protons = number of electrons. It is denoted by Z. (0.5 Mark)
Mass number = number of protons + number of neutrons. It is denoted by A. (0.5 Mark)
For example : Carbon atom its, Number of proton = 6
Number of neutrons = 6
Number of electron = 6
Atomic number(Z) = number of protons = number of electrons = 6. (0.5 Mark)
Mass number(A) = number of proton + number of neutrons = 6 + 6 =12 (0.5 Mark)