Magnesium (Mg) and chlorine (Cl) form ions through the transfer of electrons, resulting in the formation of positively charged magnesium ions (Mg²⁺) and negatively charged chloride ions (Cl⁻). This process, known as ionic bonding, occurs due to the difference in electronegativity between the two elements.

1. Electron Transfer:

- Magnesium has a low electronegativity, meaning it has a weak attraction for electrons.

- Chlorine has a high electronegativity, meaning it has a strong attraction for electrons.

2. Ion Formation:

- To achieve a more stable electron configuration, magnesium tends to lose two electrons from its outermost energy level (3s²).

- Chlorine tends to gain one electron to fill its outermost energy level (3s²3p⁵).

- As a result, magnesium loses two electrons to chlorine, forming Mg²⁺ ions and Cl⁻ ions.

The overall ionic equation for the formation of magnesium chloride can be represented as:

```

Mg (neutral) → Mg²⁺ (cation) + 2e⁻

2Cl (neutral) + 2e⁻ → 2Cl⁻ (anion)

Overall: Mg + 2Cl → Mg²⁺ + 2Cl⁻

```

The electrostatic attraction between the positively charged magnesium ions and negatively charged chloride ions holds the ionic compound, magnesium chloride (MgCl₂), together in a stable crystalline lattice structure.