"Aluminate" is not a specific chemical compound, but rather a polyatomic ion. This means it's a group of atoms that act as a single unit with an overall charge.

Here's the breakdown:

* Formula: The most common aluminate ion is AlO₂⁻, also known as tetrahydroxoaluminate(III) ion. It has a charge of -1.

* Valency: The valency of the aluminate ion (AlO₂⁻) is -1. This refers to its ability to combine with other ions to form neutral compounds.

Note: There are other aluminate ions, such as Al(OH)₄⁻, with different chemical formulas and valencies, but AlO₂⁻ is the most common.

Let me know if you have any other questions about aluminates or other chemical ions!