Question

What do you understand by atomic number and mass number?

Answer 1

Atomic number

• The number of protons present in the nucleus is equal to the atomic number (z).
• For example, the number of protons in the hydrogen nucleus is 1, in a sodium atom it is 11, therefore, their atomic numbers are 1 and 11.
• Atomic Number (z) = Number of protons in the nucleus of an atom.

= Number of electrons in a neutral atom.

Mass Number

• Mass Number is the number of protons and neutrons present in the nucleus collectively known as nucleons.
• The total number of nucleons is termed as the mass number (A) of the atom.
• Mass Number (A) = Number of protons (p) + Number of neutrons (n).