Predict the formulae of the stable binary compounds that would be formed by the combination of the following pairs of elements.
Aluminium and iodine

Explanation

To predict the formula of the stable binary compound formed by the combination of aluminum and iodine, we can follow these steps:

### Step 1: Determine the Valencies
- **Aluminum (Al)** has a valency of +3. This means it can lose three electrons to achieve a stable electron configuration.
- **Iodine (I)** has a valency of -1. This means it can gain one electron to achieve a stable electron configuration.

### Step 2: Use the Crisscross Method
- In the crisscross method, we take the absolute value of the valency of each element and cross them to determine the number of atoms of each element in the compound.
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