Two hypothetical elements X and Y have bond dissociation energies E(X-X) = 150, E(Y-Y) = 240 and E(X-Y) = 300 kJ/mol. Use Pauling's relation |chi_X - chi_Y| = sqrtDelta with Delta in eV (1 eV = 96.5 kJ/mol) and note that X is the less electronegative element. If chi_Y = 3.10, the electronegativity of X is nearest to

JEE Advanced levelSingle correct optionDifficulty 3 of 3pt181

Two hypothetical elements X and Y have bond dissociation energies $E (X - X) = 150$ , $E (Y - Y) = 240$ and $E (X - Y) = 300$ kJ/mol. Use Pauling's relation $∣ χ_{X} - χ_{Y} ∣ = Δ$ with $Δ$ in eV ( $1 eV = 96.5$ kJ/mol) and note that X is the less electronegative element. If $χ_{Y} = 3.10$ , the electronegativity of X is nearest to

The geometric mean is

150 \times 240 = 189.7

kJ/mol, so

Δ = 300 - 189.7 = 110.3

kJ/mol

= 1.143

eV and

∣Δ χ ∣ = 1.07

. Since X is the less electronegative partner,

χ_{X} = 3.10 - 1.07 = 2.03

. The value 4.17 adds instead of subtracting.