Each atom consists of a nucleus and electrons. A nucleus is the core of an atom. It consists of particles called protons and neutrons. These particles are known as nucleons as they are found int he nucleus and each has almost the same mass.

  • Atoms are mostly empty space. The nucleus contains 99.95% of the atom’s mass but only a tenth-billionth part of its volume. Practically all the mass of an atom is the mass of its nucleus.


A proton, a constituent of every atomic nucleus, is a stable sub-atomic particle that has a unit-positive electric charge (i.e. 1.60 x 10-19 C) and a rest mass of 1.67 x 10-27 kg.

A neutron, a constituent of every atomic nucleus except ordinary hydrogen, is a stable sub-atomic particle that has no electric charge and a rest mass of 1.67 x 10-27 kg.

Protons and neutrons are in the nucleus and are called nucleons.


Do you know?

The proton and the neutrons are made of much smaller particles, called quarks. You might ask: are they themselves made by even smaller particles? Physicists are proposing that everything in the Universe might be made up of tiny, vibrating closed strings. If you are interested, do a google search on string theory.


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