Read Electronegativity as a Bonded-Atom Property, Not a Fixed Constant
Electronegativity, unlike ionisation energy, isn't a single fixed number for an isolated atom — it's a property of an atom AS BONDED, and can genuinely change with oxidation state, the specific compound, and even which molecule is being compared.
Electronegativity Scale and Dependence on Bonding is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Mulliken's formula connects EN to IE and EA directly
EN (Mulliken scale) = (IE + EA)/2, so given F's IE = 17.42 eV and EA = 3.45 eV, its electronegativity works out to (17.42+3.45)/2 ≈ 10.4 on that scale — this formula lets you compute (not just recall) electronegativity whenever IE and EA values are given directly.
Electronegativity rises with oxidation state on the same element
Antimony's electronegativity in SbF₅ (Sb at +5) is higher than in SbF₃ (Sb at +3) — the same element becomes MORE electronegative as its own oxidation state rises, since a higher positive charge pulls bonding electron density toward itself more strongly. Don't treat electronegativity as one fixed value per element.
Electronegativity of a central atom depends on its ligands too
Xe's effective electronegativity is higher in XeO₃ than in XeF₂ or XeF₄ — the specific bonding environment (which atoms Xe is bonded to, and how many) shifts the electron density distribution and hence the effective electronegativity of the central atom itself.
On the Pauling scale, oxygen sits right after fluorine
F (3.98) > O (3.44) > N ≈ Cl (~3.0) — this specific ordering, with oxygen as the second-most electronegative element overall, is worth memorising directly since it doesn't follow simply from period/group position alone (Cl, despite being in the same group as F, ranks well below O).
OlympIQ exam lens
- ✓Mulliken electronegativity = (IE + EA)/2 — compute it directly when both values are given.
- ✓The same element's electronegativity rises with its own oxidation state (Sb in SbF₅ > Sb in SbF₃).
- ✓A central atom's effective electronegativity depends on which ligands it's bonded to, not just which element it is.
- ✓Pauling scale order: F > O > N ≈ Cl — oxygen ranks second overall, ahead of chlorine despite chlorine being in fluorine's own group.
Don't treat electronegativity as a single fixed number per element the way ionisation energy is — it genuinely shifts with oxidation state and bonding environment, so 'electronegativity of Sb' or 'electronegativity of Xe' needs the specific compound specified.
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