Question

Difference between atomic number and mass number

Answer 1

Hint: In chemistry many terms like atomic mass, mass number, atomic number, isotopes, isobars, etc. are very confusing because students always think all are same if an element, but these differ in some way .These are define two characteristics each and every elements of the periodic table, even same element vary with number of neutrons (isotopes) which are discussed later in details.

Complete answer:
Here, we will define the terms and make the difference between them which have been asked in the given question.
Inside an atom there exists a nucleus. This nucleus is made up of protons (+vely charged) and neutrons (neutral) and around this nucleus electrons (-vely charged) revolve in the circular orbit where the number of protons and electrons are the same to maintain electrical neutrality.
Atomic number- The atomic number of an element is equal to the number of protons in the nucleus of the atom. The elements are arranged according to their atomic number in the periodic table if we go column wise. The boron atom has atomic number 5 which means that it has 5 protons in its nucleus.
Atomic mass- The atomic mass of an element is equal to the sum of its protons and neutrons.
The difference between them is that atomic number is only the count of protons while atomic mass is the sum of both protons and neutrons.

Note:
Isotopes are the element which have the same number of protons but they have different numbers of neutrons means that the atomic number of isotopes are same but they have different mass numbers. For example, a hydrogen atom has three isotopes named protium with neutron = 0, deuterium with neutron = 1 and tritium with neutron = 2.