Question

How do you find the mass number and atomic number?

Answer 1

Hint: We know that atomic number is the identification of every element. None of the two elements have the same atomic number. The elements in the periodic table are arranged on the basis of increasing atomic number.

Complete step by step answer:
Let’s learn about atoms in detail. Atoms are the smallest unit of any matter. There are three subatomic particles of atoms namely, proton, electron and neutron. The nucleus is the centre of atoms. Protons and neutrons are present in the nucleus and electrons are present in orbits surrounding the nucleus. The proton is positively charged, the neutron is neutral and the electron is negatively charged.
Atomic number of elements is the number of protons present in the nucleus. In ground state, the number of protons and electrons is equal. For example, the number of protons and electrons present in a sodium atom is 11. But, in sodium ion $\left( {{\text{N}}{{\text{a}}^ + }} \right)$ the number of protons is 11 but the number of electrons is 10 (one electron lost).
Let’s learn about the mass number. The summation of the number of protons and neutrons of an atom gives the mass number. It is symbolically represented by ‘A’. So, the formula to calculate nuclear charge or mass number is,
Mass number=Number of protons + number of neutrons

Note: It is to be remembered that an element is represented chemically by using both the atomic number and mass number. The chemical representation of an element X is ${}_{\text{Z}}^{\text{A}}{\text{X}}$ , where A is mass number and Z is atomic number.