Which of the following is a correct formula unit of an ionic compound?

Al2F3

Ca2O

Ca (OH) 2

KCl2

Answer : The correct formula unit of an ionic compound is Ca (OH) 2

Explanation:

An ionic compound is formed when a metal atom donates one or more electrons to a non metal atom.

During this process, metal gains a positive charge and a nonmetal gets a negative charge.

In an ionic compound, these charges on the ions are balanced so that the overall compound is neutral.

Let us check which of the given compounds have a neutral charge.

1) Al2F3 : Charge on Al is + 3 and that on F is - 1.

The total charge on 2 Al is 2x3 = + 6.

The total charge on 3 F atoms is 3x (-1) = - 3

The overall charge on the compound is + 6-3 = + 3.

That means the given formula unit is not correct.

2) Ca2O : Charge on Ca is + 2 and that on O is - 2

Total charge on Ca is 2x2 = + 4

The overall charge is + 4-2 = + 2

Therefore the given formula unit is not correct.

3) Ca (OH) 2 : The charge on Ca ion is + 2 and that on OH is - 1.

The total charge on 2 OH ions is 2x (-1) = - 2

The overall charge is + 2-2 = 0

This gives a neutral compound.

Therefore the given formula unit is correct.

The answer is C)

Ca (OH) 2

I took the test and it was correct