SOLUTION

Atoms are uncharged. The number of protons in an atom is the same as the number of electrons  If an atom either gains or loses an electron, it will become electrically charged. 

When an atom loses or gains electrons, it becomes electrically charged and is called an ion. An ion is an electrically charged atom formed by the loss or gain of one or more electrons.

If an atom gains one or more electrons, it becomes a negatively charged ion; an excess negative charge is present because of electrons outnumber protons.

If an atom loses one or more electrons, it becomes a positively charged ion; more protons are present than electrons. There is an excess positive charge.

Note that the excess positive charge associated with a positive ion is never caused by proton gain but always by electron loss. If the number of protons remains constant and the number of electrons decreases, the result is a net positive charge. The number of protons, which determines the identity of an element, never changes during ion formation. 

The charge on an ion depends on the number of electrons that are lost or gained. Loss of one, two, or three electrons gives ions with 1+. 2+, or 3+ charges, respectively. A gain of one, two, or three electrons gives ions with 1-, 2-, or 3- charges, respectively.