When chlorine becomes the chloride ion, what is its charge?

Hint: remember that chlorine is a non-metal. Non-metals usually gain electrons and they become anions. An atom loses or gains an electron to achieve a noble gas configuration. The non-metals have higher electronegativity but when they become ions their electronegativity decreases and in some, there is no electronegativity at all.

Complete answer:
When a chlorine atom becomes a chloride ion it can have either a positive or negative charge. An ion is a charged atom or an atom that has either lost or gained an electron. If an ion loses an electron it attains a positive charge and when it gains an electron it attains a negative charge. An atom forms an ion to achieve a noble gas configuration.
Usually, metals easily lose electrons more easily than nonmetals, and so they become positive ions or cations. Non-metals usually gain electrons and they become negatively charged or anion.
Using the above concept we can say whether the chloride will be anion or cation. As we know, chloride is non-metal. There is an addition of an electron in its valence shell, due to which the chlorine atoms gain a negative charge and become a chloride ion.
The addition of electron in chlorine atom to become chloride ion takes place in following manner:
 $ \dfrac{1}{2}C{l_2}(g) + {e^ - } \to C{l^ - } $
Therefore chloride gains a negative charge.
This is a redox reaction. By gaining an electron, the chloride ion achieves a noble gas configuration. The chloride ions are colorless in an aqueous solution. They are low in electronegativity.

Note:
In nature, chloride is found primarily in seawater. Most chloride salts are soluble in water, thus, chloride-containing minerals are usually only found in abundance in dry climates or deep underground. It is also found in evaporite minerals such as chlorapatite and sodalite.