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.
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 |
The formula of sulphuric acid is H2SO4 and the formula of metal chloride is MCl3. Write the formula of metal sulphate.
Valency of SO4–2 is –2 and that of metal is +3 [since it combines with 3 chloride ions (–1)].
∴
Metal sulphate = M2(SO4)3.
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