Ions are charged particles that form when atoms gain or lose electrons. The process of ion formation can lead to the creation of positive ions (cations) or negative ions (anions), depending on whether electrons are lost or gained.
Formation of Positive Ions (Cations)
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Electron Loss: An atom can become a cation by losing one or more of its electrons. This often occurs with metals, which generally have few electrons in their outermost shell.
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Stable Electron Configuration: When a metal atom loses an electron, it typically does so to achieve a more stable electron configuration, often resembling that of a noble gas. For instance, sodium (Na) has an electron configuration of 1s² 2s² 2p⁶ 3s¹. By losing one electron (the 3s¹), it achieves the stable configuration of neon (1s² 2s² 2p⁶).
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Resulting Charge: Once one or more electrons are lost, the atom becomes positively charged because the number of protons (which carry a positive charge) exceeds the number of electrons (which carry a negative charge). For example, Na becomes Na⁺ when it loses one electron.
Formation of Negative Ions (Anions)
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Electron Gain: An atom can become an anion by gaining one or more electrons. This process usually occurs with nonmetals, which tend to have empty or nearly empty outer electron shells and are more likely to gain electrons to achieve stability.
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Achieving Stability: When a nonmetal atom gains an electron, it aims to achieve a stable electron configuration similar to that of a noble gas. For example, chlorine (Cl) has an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁵. By gaining one electron, it attains the stable configuration of argon (1s² 2s² 2p⁶ 3s² 3p⁶).
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Resulting Charge: The addition of electrons results in a negative charge since the number of electrons exceeds the number of protons. For instance, Cl becomes Cl⁻ when it gains one electron.
Summary
- Cations are formed by losing electrons, resulting in a positive charge, often seen in metals.
- Anions are formed by gaining electrons, resulting in a negative charge, often seen in nonmetals.
These processes are fundamental to the formation of ionic compounds, where cations and anions interact due to their opposite charges.
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