An element X is placed in group IA of the periodic table because it forms:

1. An oxide which is acid

2. A volatile chloride having formula XCl₂

3. An ionic chloride having formula XCl

4. An insoluble chloride XCl₄

Which of the following two are isostructural? 

1. XeF₂, and IF₂^-

2. NH₃, and BF₃

3. CO₂, and SiO₂

4. PCl₅, and IF₅

The dielectric constant of H₂O is 80. The electrostatic force of attraction between Na⁺ and Cl^- will be

1. reduced to $\frac{1}{40}$ in water than in air

2. reduced to $\frac{1}{80}$ in water than in air

3. will be increased to 80 in water than in air

4. will remain unchanged

Which of the following is isoelectronic? 

1. ${\mathrm{CO}}_2, {\mathrm{NO}}_2$

2. ${\mathrm{NO}}_2^{-}, {\mathrm{CO}}_2$

3. ${\mathrm{CN}}^{-}, \mathrm{CO}$

4. ${\mathrm{SO}}_2, {\mathrm{CO}}_2$

The isostere pair is

1. CO₂ and N₂O

2. CO and N₂

3. O₂ and NO₂

4. Both (1) and (2)