1) Formation of Ions

Essential Information

• Ions are charged particles that can be single atoms (e.g., Na⁺) or groups of atoms (e.g., NO₃⁻).

• Atoms form ions by gaining or losing electrons to achieve a full outer shell, similar to the electron configuration of a noble gas.

• Metals lose electrons to form positive ions (cations), while non-metals gain electrons to form negative ions(anions).

• The number of electrons lost or gained determines the charge of the ion.

Ions and Electron Transfer

1. Ions are formed when atoms lose or gain electrons.

2. Atoms lose or gain electrons to get a full outer shell, like a noble gas.

3. Metals (Group 1 and 2) lose electrons to form positive ions (e.g., Na⁺, Mg²⁺).

4. Non-metals (Group 6 and 7) gain electrons to form negative ions (e.g., Cl⁻, O²⁻).

5. The charge on an ion equals the number of electrons lost or gained.

Groups 1, 2, 6, and 7: Ion Formation

1. Elements in Groups 1 and 2 are metals that lose electrons to form positive ions (cations).

   • Group 1: +1 ions (e.g., Na⁺).

   • Group 2: +2 ions (e.g., Mg²⁺).

2. Elements in Groups 6 and 7 are non-metals that gain electrons to form negative ions (anions).

   • Group 6: 2- ions (e.g., O²⁻).

   • Group 7: 1- ions (e.g., Cl⁻).

3. Ions formed by elements in the same group have the same charge because they lose or gain the same number of electrons.

Examples of Ion Formation

1. Sodium (Na) is in Group 1:

   • It loses 1 electron to form a Na⁺ ion with the same electron configuration as neon:

   • Na → Na⁺ + e⁻.

2. Magnesium (Mg) is in Group 2:

   • It loses 2 electrons to form a Mg²⁺ ion with the same electron configuration as neon:

   • Mg → Mg²⁺ + 2e⁻.

3. Chlorine (Cl) is in Group 7:

   • It gains 1 electron to form a Cl⁻ ion with the same electron configuration as argon:

   • Cl + e⁻ → Cl⁻.

4. Oxygen (O) is in Group 6:

   • It gains 2 electrons to form an O²⁻ ion with the same electron configuration as neon:

   • O + 2e⁻ → O²⁻.