Question

What does the atomic number of an element indicate?

Answer 1

Hint: Each element possesses different chemical properties and these different properties arise due to the difference in the composition and arrangement of atoms of the element. Elements have a unique set of protons in their nucleus which is denoted by their atomic numbers.

Complete answer:
An element is a pure substance that consists of the same type of atoms. Atoms of different elements contain a different set of subatomic particles, that are electrons, protons, and neutrons. Neutrons and protons are found in the nucleus of the atom while electron is found outside the nucleus in the atomic orbitals. Out of all these subatomic particles, the number of protons is unique for each element. Elements are differentiated and observed by the number of protons present inside them.
The number of protons in the nucleus of each atom of an element is known as the atomic number. It is the characteristic property of any element and is denoted by the letter Z. The modern periodic table is also arranged in increasing order of atomic numbers of elements.
For neutral atoms or elements, the atomic number indicates the number of protons as well as the number of electrons because the number of protons must be equal to the number of electrons to maintain the electroneutrality of the element.
For example, carbon has 6 protons in its nucleus. It means that the atomic number of carbon is 6.
Hence, the atomic number of an element indicates the number of protons as well as the number of electrons present in its nucleus.

Note:
Few elements possess the same number of protons but differ in the numbers of neutrons. Such pairs of elements are called isotopes. Also, some elements have the same mass number (number of protons plus number of neutrons) but a different number of protons. These are known as isobars.