Atom is smallest unit of any element. It consist of 3 subatomic particles known as protons,electrons and neutrons. Protons and neutrons are present inside the nucleus and electrons are always moving outside the nucleus on to the shells. Protons are positive charge, neutrons are neutral and electrons are always negatively charge particles. In an atoms number of protons are always equal to number of electrons. For example, helium is an element with the symbol 'He' and an atomic number of 2, indicating that it has 2 protons and 2 electrons.

Posted By: Sonal