100 points! formation of an ion

aluminum is one of the most common elements in earth's crust, yet it is never found as a pure element in nature. that is, aluminum atoms are always combined with atoms of other elements, such as oxygen. an aluminum oxide compound you will recognize by its name is the gemstone called "ruby". its chemical formula is

al2o3

if every oxygen ion (combined with an aluminum ion) has a charge of -2, what must the charge of each aluminum ion be? how can you tell this? also, what has to happen to an uncharged aluminum atom so that it will bond with oxygen?

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