Question

Which of the following statements are true?

1. Unlike Ga that has a very high melting point, Cs has a very low melting point.
2. On Pauling scale, the electronegativity values of N and Cl are not the same.
3. Ar, K⁺, Cl⁻, Ca²⁺ and S²⁻ are all isoelectronic species.
4. The correct order of the first ionisation enthalpies of Na, Mg, Al, and Si is Si > Al > Mg > Na.
5. The atomic radius of Cs is greater than that of Li and Rb.

Choose the correct answer from the options given below:

Options

• A, B and E only

• C and E only

• C and D only

• A, Cand E only

Answer 1

C and E only

Explanation:

Ca²⁺, K⁺, Ar, Cl⁻, and S²⁻ are all isoelectronic species, as they possess 18 electrons.

Caesium (Cs) has a larger atomic radius than both lithium (Li) and rubidium (Rb). This is because the atomic radius typically increases as one moves down a group in the periodic table. The final element in group 1 is Cs, which is preceded by both Li and Rb. The order of atomic radius in group I is as follows:

Cs > Rb > K > Na > Li