Question

20. Define
(a) atomic number and
(b) mass number​

Answer 1

Mass Number :

It is the total number of protons and neutrons in the nucleus

Atomic number:

The number of protons in the nucleus of an atom of an element and characterise his place in the periodic table

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Answer 2

Answer:

ATOMIC NO.

The atomic number of an atom is the no. of protons in the nucleus of an atom.

MASS NO.

The mass number is defined as the total number of protons and neutrons in an atom.