Question

Aluminum hydroxide is a popular antacid. What is the formula of aluminum hydroxide?

Answer 1

Aluminum is on the third column after the previous noble gas (`"Ne"`). In order to achieve a full valence shell, it can lose `3` valence electrons to become `"Al"^(3+)`.

In return, it wants neutrality. Each `"OH"^(-)` contributes a `-1` charge, so to balance out a `+3` charge, you need `3xx"OH"^(-)`.

So, the product of the following combination is aluminum hydroxide:

`"Al"^(3+) + 3"OH"^(-) -> bb("Al"("OH")_3)`

Note how the charges balance out. `+3 + (3xx -1) = 0`.