Valency of Aluminium is

 3

To understand the valency of aluminium, we need to analyze its atomic structure:

• Atomic Number (Z): Aluminium has an atomic number of 13.
• Electronic Configuration: The electronic configuration of aluminium is 2, 8, 3.

Explanation:

• Valency refers to the ability of an atom to combine with other atoms by losing, gaining, or sharing electrons.
• For aluminium, the outermost shell contains 3 electrons.
• To achieve a stable electronic configuration, aluminium tends to lose these 3 electrons.
• As a result, the valency of aluminium is +3, which is also written as 3.

Thus, the valency of aluminium is 3.