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An ion is formed when an atom gains or loses an electron in bonding with another atom, causing the atom to become a positive or negative ion. Since electrons are negative, if an atom loses an electron, there are more protons (which are positive) than electrons, which causes the atom to become a positive ion (sometimes called a cation.) If an atom gains an electron it becomes a negative ion (or anion.) Ions are most commonly formed when two elements undergo ionic bonding, in which the elements 'give and take' electrons to gain full outer shells.

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16y ago

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