Question

How are the atomic number and mass number related to the number of neutrons and protons inside an atom?

Answer 1

Atomic number

• The atomic number of an element is equal to the number of protons present inside the nucleus of its atom.

Atomic number(Z) = Number of protons(P) inside the nucleus of an atom of that element.

Mass number

• The mass number of the atom of an element is equal to the sum of the number of protons and the number of neutrons present in its nucleus.

Mass number(A) = Number of protons(P) + Number of neutrons(N).

Example: ${\mathrm{C}}_6^{12}$

• Atomic number = 6 , therefore number of protons = 6 = Number of electron.
• Mass number = 12.
• The number of neutrons = Mass number - Number of protons.

= 12 - 6

• The number of neutrons = 6.