Question

Molecular formula of the chloride of an element X is XCl. This compound is solid and has a high melting point. Write the name of any element present in the same group as X.

Answer 1

Hint: It is known that chlorine is a highly electronegative compound. Thus, the highly electropositive element must be attached to chlorine to acquire an ionic bond. when the element is highly electronegative, it means it has a high tendency of attraction of a shared pair of electrons towards itself.

Complete step by step answer:
On moving down the group, electronegativity decreases, and on moving from left to right across the periodic table, electronegativity increases.
From left to right across the periodic table, the halogens family has the highest electronegativity character. Fluorine is the highest electronegative element on the periodic table.
 When one of the elements in the compound is highly electronegative, then the other elements must be highly electropositive. Among the groups in the periodic table, alkali metals are highly electropositive since it readily loses its valence shell of one electron to attain noble gas configuration.
Therefore, for the XCl compound, X may be alkali metals or hydrogen, since hydrogen is also highly electropositive.
If X-Any alkali metals, then compound obtained is salt since it is obtained from the neutralization of strong base and strong acid{Hydrochloric acid}
Eg: NaCl [Salt] is obtained as, \[NaOH + HCl \to NaCl + {H_2}O\]
Generally, the greater the charge on the ions, the stronger is the forces binding them together and it leads to the high melting point. Alkali metals possess a strong melting point.
Thus, in XCl X-Any alkali metals
The alkali metals are Lithium, Sodium, Potassium, Rubidium, Caesium, and Francium.

Note: In XCl, X cannot be Hydrogen as HCl is a liquid and not a solid. If X-HCl, then the compound hydrochloric acid is a highly corrosive liquid. Alkali metals exist as salt. Thus, in XCl, X are alkali metals.