Symbol represents an ion?

The numbers, positive, negative signs and the symbol of elements are used to represent the ions.

Explanation:

Steps to write the ions:

Write the symbol of an element. For example in case of magnesium we would write Mg. In second step write the number of electrons in superscript that are lost or gained by an atom. For example magnesium atom loses two electrons written as followed, Mg². In third step write the charge as superscript after the numbers. For example, magnesium loses two electrons that's why we put the positive sign after 2, because by losing the electrons cations are formed. Mg²⁺ If the atom of an element lose or gain only one electron then 1 is omitted and only the negative or positive sign are written on superscript. For example in case of sodium cation and chlorine anion, Na⁺, Cl⁻.