The correct decreasing order of first ionisation enthalpies of five elements of the second period is

• Be > B > C > N > F

• N > F > C > B > Be

• F > N > C > Be > B

• N > F > B > C > Be

The first () and second (ΔH₂) ionisation enthalpies (in kJ mol^-1) and the (Δ_egH) electron gain enthalpy (in kJ mol^-1) of the elements I, II, III, IV and V are given below

The most reactive metal and the least reactive non-metal of these are respectively

• I and IV

• IV and II

• II and IV

• III and IV

243.

'Hydride Gap' is referred to which region of the Periodic Table ?

• Groups 3, 4 and 5

• Groups 5, 6 and 7

• Groups 4, 5 and 6

• Groups 7, 8 and 9

The electronic configuration of the element with maximum electron affinity is

• 1s², 2s²,2p³

• 1s², 2s²,2p⁵

• 1s², 2s²,2p⁶, 3s², 3p⁵

• 1s², 2s²,2p⁶, 3s², 3p³

The first ionisation energy of oxygen is less than that of nitrogen. Which of the following is the correct reason for this observation?

• Lesser effective nuclear charge of oxygen than nitrogen.

• Lesser atomic size of oxygen than nitrogen

• Greater interelectron repulsion between two electrons in the same p-orbital counter balances the increase in effective nuclear charge on moving from nitrogen to oxygen.

• Greater effective nuclear charge of oxygen than nitrogen.

The correct match of contents in Column I with those in Column II is

• A-iv, B-i, C-ii, D-iii

• A-iii, B-i, C-ii, D-iv

• A-iv, B-iii, C-ii, D-i

• A-ii, B-iv, C-i, D-iii

The lattice enthalpy and hydration enthalpy of four compounds are given below

The pair of compound which is soluble in water is

• P and R

• Q and R

• P and Q

• Rand S

In which of the following the oxidation number of oxygen has been arranged in increasing order?

• OF₂ < KO₂ < BaO₂ < O₃

• BaO₂ < KO₂  < O₃ < OF₂ 

• BaO₂  < O₃ < OF₂  < KO₂ 

•  KO₂  < OF₂  < O₃ < BaO₂ 

In which one of the following pairs the radius of the second species is greater than that of the first?

• Na, Mg

• O^2-, N^3-

• Li⁺, Be²⁺

• Ba²⁺, Sr²⁺

The one electron species having ionization energy of 54.4 eV is :

• H

• He⁺

• B⁴⁺

• Li²⁺