Question

How do We determine the atomic number of an element$?$

Answer 1

Atomic number is characteristic of a chemical element and determines its place in the periodic table and can be calculated in various possible ways. Consider the various constituents of an atom present in an element and try to determine the atomic number of an element from there.

Complete step-by-step answer:
Atoms are the building blocks of matter. They combine in numerous patterns and form different substances. All atoms except the common form of hydrogen contain protons, neutrons and electrons. In a neutral atom, the number of protons is equal to the number of electrons present in the shells that is the energy level around the nucleus. The number of protons determines an element’s atomic number $\left( Z \right)$ and distinguishes one element from another.

Therefore the atomic number of an element is defined as the number of protons found in the nucleus of every atom of that element. For example: The atomic number of $C$ is $6$because there are $6$ protons in the nucleus of an atom.

Additional Information: If the mass number of an element and the number of neutrons present in the nucleus of the atom is given we can calculate the atomic number as,
$Mass\,Number\, = \,Atomic\,Number + Number\,of\,neutrons$. Hence by manipulating the equation a bit we can get the atomic number of the element.

Note: We can also calculate the atomic number of an element if the number of electrons is given for the element as to maintain the neutrality of an element number of electrons is equal to the number of protons present in the atom. Hence the atomic number is also equal to the number of electrons present in the atom.