Question 1

Electronegativity is the tendency of an atom in a molecule to:

Accepted Answer

Attract the shared pair of bonding electrons towards itself. It is a relative measure of an atom's pull on the shared electrons in a covalent bond.

Question 2

Across a period, electronegativity generally:

Accepted Answer

Increases. Rising Z_eff and smaller size increase the pull on shared electrons.

Question 3

Down a group, electronegativity generally:

Accepted Answer

Decreases. Larger size and shielding reduce the attraction for shared electrons.

Question 4

The most electronegative element is:

Accepted Answer

Fluorine. F has the highest electronegativity (4.0 on the Pauling scale).

Question 5

The Mulliken electronegativity is defined as:

Accepted Answer

χ_M = (IE + EA)/2. Mulliken took the average of ionization energy and electron affinity (in eV).

Question 6

On the Pauling scale, the electronegativity difference is related to the extra bond energy Δ by:

Accepted Answer

|χ_A − χ_B| = 0.208√Δ (Δ in kcal/mol). Pauling: |χ_A − χ_B| = 0.208√Δ, where Δ is the resonance (ionic) contribution to the bond energy.

Question 7

The difference between electronegativity and electron gain enthalpy is that electronegativity:

Accepted Answer

Is a property of a bonded atom (relative), while electron gain enthalpy is for an isolated gaseous atom. Electronegativity is a relative, dimensionless bonding property; Δₑ𝓰H is a measurable enthalpy for a free atom.

Question 8

A diagonal relationship exists between pairs such as:

Accepted Answer

Li–Mg, Be–Al, B–Si. Diagonally placed elements show similar properties (Li–Mg, Be–Al, B–Si).

Question 9

The cause of the diagonal relationship is the similarity in:

Accepted Answer

Charge/radius ratio (polarising power). Moving right increases charge and moving down increases size; diagonally these offset to give similar charge/size ratios.

Question 10

Across a period, metallic character:

Accepted Answer

Decreases (non-metallic character increases). Higher IE and electronegativity across a period make elements less metallic.

Question 11

Down a group, metallic character:

Accepted Answer

Increases. Lower IE down a group makes it easier to lose electrons — more metallic.

Question 12

The nature of oxides across a period changes in the order:

Accepted Answer

Basic → amphoteric → acidic. e.g. Na₂O (basic) → Al₂O₃ (amphoteric) → Cl₂O₇ (acidic).

Question 13

Down a group, the basic character of the oxides/hydroxides of the elements:

Accepted Answer

Increases. Greater metallic character down a group gives more basic oxides/hydroxides.

Question 14

The valency of an element with respect to hydrogen for group 15 is:

Accepted Answer

3. H-valency = 8 − group(old, i.e. 8 − 5) = 3, e.g. NH₃.

Question 15

Al₂O₃ is classified as ______ because it reacts with both acids and bases:

Accepted Answer

Amphoteric. Amphoteric oxides (Al₂O₃, ZnO, PbO) react with both acids and bases.

Question 16

The Allred–Rochow scale of electronegativity is based on the:

Accepted Answer

Electrostatic force exerted by the nucleus on the valence electrons. Allred–Rochow: χ ∝ Z_eff/r², the effective nuclear pull on a valence electron.

Question 17

The correct increasing order of electronegativity for C, N, O, F is:

Accepted Answer

C < N < O < F. Electronegativity increases across a period: C < N < O < F.

Question 18

The Mulliken electronegativity (in eV) of an atom with IE = 17.4 eV and EA = 3.6 eV is:

Accepted Answer

10.5 eV. χ_M = (IE + EA)/2 = (17.4 + 3.6)/2 = 10.5 eV.

Question 19

For a bond A–B with an ionic resonance energy Δ = 100 kcal/mol, the electronegativity difference (Pauling) is:

Accepted Answer

2.08. |χ_A − χ_B| = 0.208√Δ = 0.208 × 10 = 2.08.

Question 20

The correct decreasing order of electronegativity for F, Cl, Br, I is:

Accepted Answer

F > Cl > Br > I. Electronegativity decreases down group 17: F > Cl > Br > I.

Electronegativity, Reactivity & Anomalous Properties — JEE Main Chemistry MCQs with Solutions

Questions with solutions