Question

Elaborate the terms mass number and atomic mass.Explain the difference between the two.

Answer 1

• Mass number is the sum of number of protons and neutrons in an atom.
• Atomic mass of an atom is the sum of masses of protons, electrons and neutrons in that atom.

Mass number	Atomic mass
Mass number is the sum of number of protons and neutrons in an atom.	Atomic mass is also known as atomic weight. It is the weighted average mass of an atom of an element based on the relative abundance of that element's isotopes.
Being a count of numbers it will be a whole number	Being the average mass of different isotopes of an atom this will be a decimal number number.
Mass number is not variable for a given atom.	Atomic mass can be variable with the change in relative abundance of isotopes
Mass number of protium will be 1 as it does not have any neutrons but that of deuterium will be 2 as it has a neutron as well.	eg; Hydrogen has 3 different isotopes called protium, deuterium and tritium.The atomic mass will be the average of their mass relative to their natural abundance.Atomic mass=1.00784g/mol.