Protons, electrons and neutrons are the main constituents of an atom. Every form of matter is a combination of fixed numbers of these constituents. So, for understanding matter world, we must know the number of protons, electrons and neutrons in an atom and its significance.Finding the number of protons, electrons and neutrons

How to Find the Number of Protons, Electrons and Neutrons in an Atom?

These three sub-atomic particles are responsible for almost all the properties of an atom. Also, a change in the number of these particles in an atom may give rise to a new atom or introduces a new form of the same atom. So, knowing the number of these sub-atomic particles and the change in properties relative to the change in number provides a better understanding of the sub-atomic world.

Finding the number of protons, electrons and neutrons in an atom

You can find the number of protons in an atom easily because it is just the atomic number of the atom. If you have an aluminium atom, it will have 13 protons in each atom because its atomic number is 13. Likewise, gold has atomic number 79, so each gold atom has 79 protons in it.

An atom is electrically neutral. That means it has the same number of positive and negative charge. Since an electron carries negative charge equal to the positive charge carried by a proton in magnitude, the number of protons and electrons are the same in an atom. However, for an ion, the number of electrons may differ. For positively charged ions, the number of electrons is the number of protons minus the positive charge it has and vice-versa.

The number of neutrons and electrons in an atom may vary to a wide extent. So, to distinctly say the number of neutrons, we need a little bit more information. This information is the atomic mass. Generally, we can subtract the atomic number from the atomic mass of an atom to get the number of neutrons. Since neutrons and protons only contribute to the mass of an atom, this works well but only for whole number masses. For the non-whole number masses, we must round off the atomic mass first.

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The Significance of Number of These sub-atomic Particles

The number of sub-atomic particles is responsible for the change in properties of an atom. Change in the number of protons changes the property of the entire atom and gives a different element. Meanwhile, change in the number of electrons changes the atoms to ions, which are chemically active. The variation of the number of neutrons in an atom determines the stability of an atom. Higher the number of protons, a higher number of neutrons are required in order to make an atom stable.


Ashwin Khadka is a Physics graduate from Tribhuvan University, Kathmandu, Nepal. He is a science enthusiast, researcher and writer. Apart from writing he is also a researcher, with specialization on thin films for electrodes in solar cells.

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