Be²⁺ is isoelectronic with which of the following ions?

1. H⁺

2. Li⁺

3. Na⁺

4. Mg²⁺

The correct order of the decreasing ionic radii among the following isoelectronic species is : 

1. Ca²⁺ > K⁺ > S^2- > Cl^-

2. Cl^- > S^2- > Ca²⁺ > K⁺

3. S^2- > Cl^- > K⁺ > Ca²⁺

4. K⁺ > Ca²⁺ > Cl^- > S^2-

The correct order of increasing electron gain enthalpy with a negative sign for the elements O, S, F, and Cl is : 

1. Cl < F < S < O                   

2. O < S < F < Cl

3. F < S < O < Cl                   

4. S < O < Cl < F

Which one of the following compounds is a peroxide ?

1. KO₂

2. BaO₂

3. MnO₂

4. NO₂

The sequence of ionic mobility in aqueous solution is

1. K⁺>Na⁺>Rb⁺>Cs⁺

2. Cs⁺>Rb⁺>K⁺>Na⁺

3. Rb⁺>K⁺>Cs⁺>Na⁺

4. Na⁺>K⁺>Rb⁺>Cs⁺

Which one of the following arrangements does not give the correct picture of the trends indicated against it?

(1) F₂ > Cl₂ > Br₂ > I₂ :Oxidising power

(2) F₂ < Cl₂ > Br₂ > I₂ : Electron gain enthalpy

(3) F₂ > Cl₂ > Br₂ > I₂ : Bond dissociation energy

(4) F₂ > Cl₂ > Br₂ > I₂: Electronegativity

Identify the correct order of the size of the following:

(1) Ca²⁺<K⁺<Ar<S^2-<Cl^-

(2) Ca²⁺<K⁺<Ar<Cl^-<S^2-

(3) Ar<Ca²⁺<K⁺<Cl^-<S^2-

(4) Ca²⁺<Ar<K⁺<Cl^-<S^2-

An element whose IUPAC name is Ununtrium (Uut) belongs to:

1. s-Block elements                       

2. p-Block elements

3. d-Block elements                              

4. Inner transition elements .

Which among the following is not a representative element?

The period number and group number of "Tantalum" (Z=73) are respectively :