Which statement best defines an ion?

Which statement best defines an ion?

• A. A neutral atom
• B. An atom with an unequal number of protons and electrons
• C. A molecule with two or more atoms
• D. A charged molecule formed by sharing electrons

Answer: (B)

An ion is a charged particle formed when the number of protons and electrons is not equal. In a neutral atom, protons and electrons balance, so there is no net charge. If electrons are lost, more protons remain than electrons, giving a positive charge. If electrons are gained, there are more electrons than protons, giving a negative charge. This imbalance—unequal numbers of protons and electrons—creates the net charge that defines an ion. The other ideas don’t fit as well: a neutral atom isn’t charged, a molecule with multiple atoms isn’t necessarily charged, and sharing electrons describes bonding rather than the gain or loss of electrons that creates charge.

An ion is a charged particle formed when the number of protons and electrons is not equal. In a neutral atom, protons and electrons balance, so there is no net charge. If electrons are lost, more protons remain than electrons, giving a positive charge. If electrons are gained, there are more electrons than protons, giving a negative charge. This imbalance—unequal numbers of protons and electrons—creates the net charge that defines an ion. The other ideas don’t fit as well: a neutral atom isn’t charged, a molecule with multiple atoms isn’t necessarily charged, and sharing electrons describes bonding rather than the gain or loss of electrons that creates charge.