Question

How is the atomic number determined?

Answer 1

Atomic number:

1. The atomic number for an element is denoted by
2. The atomic number of an element is equal to the number of protons present in the nucleus of an atom.

Determination of atomic number:

1. The atomic number of an element is determined by the number of protons present in the nucleus of an atom.
2. The number of protons for the same element never changes. It always remains the same.
3. Therefore, the atomic number for the same element is unique and never changes.
4. Also, in a neutral atom number of electrons is equal to the number of protons in it.
5. Therefore, the atomic number of an element is equal to the number of electrons present in a neutral atom.
6. Thus, atomic number of an element can be determined from the number of protons or electrons in a neutral atom.

Example:

1. A neutral Oxygen $\mathbf{\left(}\mathbf{O}\mathbf{\right)}$ atom contains $8$ protons and $8$ electrons.
2. Hence, the atomic number of Oxygen is $8$.