Question

What is an atomic number? How is it used to distinguish one element from another?

Answer 1

Hint: We know that an atom is composed of three subatomic particles namely proton, electron and neutron. At the centre of an atom, a nucleus is present. Protons and neutrons are present in the nucleus and electrons are present in orbits surrounding the nucleus.

Complete step by step answer:
Let’s discuss atomic numbers in detail. The number of protons in an atom gives the atomic number of the element. It is represented by the symbol Z. For example, the atomic number of hydrogen 1 that means, there is only one proton present in hydrogen.
The atomic number of every known element is different from each other because the number of protons is different in all elements. So, an atomic number is the identification of an element and it distinguishes one element from another. But isotopes have different numbers of neutrons and equal numbers of protons. For example, Protium, deuterium and tritium are the three isotopes of hydrogen. Protium has one neutron, deuterium has two neutrons and tritium has three neutrons. But all these isotopes of hydrogen have equal numbers of protons.

Additional Information:
Neutral atoms of an element contain equal numbers of protons and neutrons. For example, a sodium atom has 11 protons and 11 electrons. But, the sodium ion $\left( {{\text{N}}{{\text{a}}^ + }} \right)$ contains 11 protons and 10 electrons.

Note: It is to be noted that the sum of the number of protons and neutrons give the mass number of an atom. The mass number is represented by the symbol A. To give the chemical symbol of an element we use both the mass number and atomic number, $_{\text{Z}}^{\text{A}}{\text{X}}$
, where X is any element.