An atom can also be defined as the smallest particle of an element is usually the smallest unit of matter made up of a central nucleus in the midst of electrons that are negatively charged.
In the atomic nucleus are protons which are positively charged, and neutrons that are electrically neutral. The electromagnetic force is the one that bind the electrons of an atom to the nucleus. When particles of the same nature are combined together they give raise to molecules and when molecules combined they produce elements. The subatomic particles that are in the nuclei of an atom or atoms are what are referred to as the neutrons. The act of nuclear fission is required so as to get rid of the neutrons from an atom. Neutrons are said to have almost the same weight as the protons.
When an atom of an element looses or gains electrons, it transforms to a charged ion. An isotope results from the loss or gain of neutrons by an element which weighs a little higher or a little lower than the average weight. A time, an atom of an element can lose or gain protons and therefore it is not regarded as the same element. As a matter of fact, it becomes an element to left or to the right of the element in the periodic table. When an atom gains neutrons, it becomes heavier and when it loses neutrons it becomes lighter. However, the charge of an atom is never affected by the loss or gain of neutrons.
An atom becomes positive after losing an electron, on the other hand it becomes negative when it loses a proton but remains a neutral atom when it loses a neutron.