Question

ii)Valency is the number of electron_____or______by an atom.

iii)Mass number is the total number of protons and_____in the nucleus of an atom.​

Answer 1

Answer:

Valency is the number of electron given or taken by an atom.

Mass number is the total number of protons and neutrons in the nucleus of an atom.

Hope it helps you...

Answer 2

Answer:

neutron and protons

Explanation:

proton and electron