Question

What is the mass number of boron?

Answer 1

Every atom has an equal number of protons and neutrons to be stable, the nucleus is the heavy portion inside the atom with protons and neutrons, outside the nucleus electrons are present. The number of nucleons i.e The sum of the proton and neutrons gives the mass number of an atom.

Complete answer:
Periodic table is the representation of chemical elements arranged in the increasing order of atomic numbers and arranged in the vertical columns and horizontal rows.
The vertical columns are called groups and the horizontal rows are called periods. There are seven periods and eighteen groups in the periodic table. The elements belonging to the group $13$ are called the Boron family. The first element in the group $13$ is Boron. The elements in that group can be called as the elements belonging to the Boron family.
Boron is the chemical element with atomic number $5$ . It has three electrons in its outermost orbital. The electronic configuration of boron is $1{s^2}2{s^2}2{p^1}$ . Thus, the number of electrons in boron is five which reveals the number of protons will also be five. But, the naturally occurring isotope of boron is $80\%$ , having the mass number $11$ . Thus, the number of neutrons is six. Thus, the mass number of boron is $11$ .

Note :
Mass number is the number of protons and neutrons, whereas atomic number is the number of only protons. The number of nucleons i.e. The number of subatomic particles in the nucleus protons and neutrons gives the mass number.