What is an ion and how are they formed?

An ion can be an atom or a group of atoms that are charged. This means they can be positively charged or negatively charged.A positive ion is formed when the atom loses electrons. Because electrons have a negative charge think of it as the atom losing a bit of negativity- and therefore becomes positively charged. For example:The atom sodium (Na) has 11 electrons. 2 electrons in its first energy shell, 8 in its second energy shell and 1 in its outermost shell. When sodium becomes an ion, it loses the outer electron to become Na⁺. A negative ion is formed when the atom gains electrons. Using the same thinking as above, if an atom gains a negatively charged electron it itself will become negative. For example, the oxygen atom has 8 electrons. 2 in its first energy shell, 6 in its outermost energy shell. To become a full outer shell, oxygen gains 2 electrons. This is 2 extra negative charges. Therefore oxygen becomes O^2-