Question

Two elements X and Y belong to group 1 and 2 respectively in the same period.
Compare them with respect to:
A.The number of valence electrons
B.Valency
C.Metallic character
D.Size of atom
E.Formulae of their oxides and chlorides

Answer 1

The number of valence electrons and valency is the same as the group number. As we move left to right the metallic character decreases.. As we move along the period, Size of the atom decreases. Formulas of oxides and chlorides can be calculated from the respective valences of each of the elements.

Complete step by step answer:
Let us compare the properties of the group 1 and 2 elements:
A.The group number of element X is 1 that is if one electron is in its valence shell. Element Y is in the group number 2 is that means it has two electrons in its valence shell.
B.Valency is the number of bonds the element can form. For group number 1 and 2 the valency remains the same. So the valence electron and the valency of the element X will be one and the valency and valence electron of the element Y will be 2.
C.As we move from Group 1 to group 2 the metallic character decreases. Group 1 elements are most metallic in nature. So X is more metallic than element Y.
D.The size of X is more than Y.
E.Oxygen has a valency of 2 and the element X has a valency of 1 according to this the formula of the oxide will be ${{\text{X}}_2}{\text{O}}$ .
The chloride ions have a valency of 1. The formula of chlorides of X will be ${\text{XCl}}$.
In the same way the formula for oxide of element Y will be ${\text{YO}}$ .
The formula for chlorides will be ${\text{YC}}{{\text{l}}_2}$ .

Note:
Group number 1 elements are known as alkali metal and group number 2 elements are known as alkaline earth metal. This is because their oxides and hydroxides are basic in nature and group number two elements are mostly found in Earth crust.