Give the name and valency of the following polyatomic ions :
Ammonium, Hydroxide, Nitrate, Carbonate, Sulphate, Sulphite, Bicarbonate, Phosphate.
Polyatomic ion |
Symbol |
Valency |
Ammonium |
(NH4)+1 |
+ 1 |
Hydroxide |
(OH)– |
–1 |
Nitrate |
(NO3)–1 |
– 1 |
Carbonate |
(CO3)–2 |
–2 |
Sulphate |
(SO4)–2 |
–2 |
Sulphite |
(SO3)–2 |
-2 |
Bicarbonate |
(HCO3)–1 |
–1 |
Phosphate |
(PO4)–3 |
-3 |
If the calcium salt of a hypothetical anion Z has the molecular formula Ca3Z2. What is the valency of Z and what would be molecular formula of the aluminium salt of Z?
In a ionic compound the charge excange, thus Valency of Z = –3
Valency of Al = +3
Formula of aluminium salt of Z = AlZ.
Do all elements have a charged valency? Explain.
All elements do not form ions so their valencies do not have a charge. For example, carbon and silicon have a valency of 4 and nitrogen has a valency of 3. Further molecules containing only non-metals are formed without a charged valency. For example, in carbon tetrachloride (CCl4), carbon has a valency of 4 and chlorine has a valency of 1.
Calcium pyrophosphate is represented by the formula Ca2P2O7. Write the formula of ferric pyrophosphate.
Calcium has a valency of +2. There are two Ca atoms. Thus Ca carries a total of +4 charges. Therefore, pyrophosphate has a valency of -4. Since ferric ion has a valency of +3, the formula of ferric pyrophosphate is Fe4(P2O7)3.