Question

What is the charge of the underlined ion in bold in the following compounds: Al(OH)3 K2SO4 ZnCl2 (d) Ca(OH)2

Answer 1

All atoms in the universe wants to become stable by completing it's octet. This can be achieved by gaining or donating electrons. Octet contains eight electrons. Minimum number of electrons should be transfer to achieve this.

(a) Al have 3+ charge on it i.e Al³⁺

Aluminium have 3 electrons in it outermost Valence shell. Al used to donate all 3 electrons to complete it's octet and because stable. Hydroxide ions in Al(OH)₃ gain one electron each and become OH^-1 so three Hydroxide ions gain total 3 electrons

(b) SO₄ have 2- charge on it i.e SO₄^2-

Potassium, K is first group element it have only one electron in it's outermost Valence shell by donating this electron it become K⁺ so two Potassium atom donate one electron each to SO₄ and make it SO₄^2-

(c) Zn have +2 charge on it i.e Zn²⁺

Chlorine, Cl have seven electrons in it's outermost Valence shell so Cl atom require only one electron to complete it's octet so in ZnCl₂ each chlorine atom gain one electron from zinc and make it Zn²⁺

(d) OH have -1 charge on it i.e OH^-

As mentioned in part (a) OH have -1 charge on it. Oxygen in OH require two electrons to complete it's octet in which one electron is already gained from Hydrogen atom.

Calcium donate one electron each to Hydroxide ion.