Question

Explain why the chemical formula for calcium hydroxide , Ca(OH)2 is not written as CaO2H2

Answer 1

It's written
`Ca(OH)_2` because of its dissociation behavior

Step-by-step explanation:

The
`OH^-` is a functional group called hydroxyl and is the product (for example) of the dissociation of water.

When formulating compounds like the
`Ca(OH)_2` called hydrides , hydroxyl groups are added like blocks to balance the valence of the other element (in this case Ca).

At the dissociation, O and H stay bonded because of the very strong afinity this atoms have and this is why they are written as a unit.

Answer 2

The formula CaO₂H₂ correctly gives the relative number of each type of atom in the compound.
But the OH group usually behaves as a unit. It doesn't fall apart.
So chemists have agreed to write the OH group as a unit: Ca(OH)₂.
This shows that there are 1 Ca atom and 2 OH groups in a formula unit of calcium hydroxide.