Question

The valency of Calcium is 2. Write the valences of the other radicals in the given compounds.
A.$\text{CaO}$
B.$\text{Ca}{{\left( \text{OH} \right)}_{2}}$
C.$\text{CaC}{{\text{O}}_{\text{3}}}$
D.$\text{CaC}{{\text{l}}_{2}}$

Answer 1

Hint:The valency of an element in a compound is defined by the combining capacity of the element or the number of electrons given by the element or taken by it during the formation of the compound. For neutral compounds, the total valency is always zero.

Complete answer:
To find out the valences of the radicals in the above compounds, it should be known that a compound is electrically neutral. In calcium oxide, the calcium is electropositive in nature and to fulfil its octet, the calcium atoms lose two electrons to form the calcium cations whose valency is 2, hence the corresponding anion, i.e. the oxide anion must also have valency 2 to balance the positive charge on the calcium cation.
In calcium hydroxide, as can be seen from the formula, the valency of calcium cation being (2), the valency of the hydroxyl radical must be equal to 1, as two of them are required to make a stable compound.
The total charge of the carbonate radical must be equal to 2 to balance the positive calcium cation and make the calcium carbonate a neutral compound.
In calcium chloride, the charge of the chloride ions should be negative to balance the positive charge on the calcium ions, and as per the formula as there are two chloride anions to balance the calcium ions, the valence of the chloride ions should be 1.

Note:
The valency of an element in a compound can be readily determined from the formula of the compound and the position of the elements in the periodic table. The tendency of the element to fulfil its octet is also a factor that is useful in determining the valency of the element.