Chemistry · Periodic Classification Of Properties · NEET
Because electronegativity is the power of an atom to pull shared electrons toward itself inside a chemical bond. It is defined only when the atom is bonded to another atom. So its value depends on the partner atom. NCERT says clearly: 'The electronegativity of any given element is not constant; it varies depending on the element to which it is bound.' It is not a property of a free single atom.
No. This is NCERT intext question 3.23. Saying N is exactly 3.0 in all compounds is wrong. 3.0 is only an average or approximate Pauling value. The real value shifts a little depending on what nitrogen is bonded to and its oxidation state. So you cannot say it is the same in every compound.
Two main reasons. (1) The bonded partner: a strong electron-pulling neighbour changes how tightly an atom holds shared electrons. (2) The oxidation state and hybridisation: an atom in a higher oxidation state, or with more s-character in its hybrid orbital, holds electrons more tightly, so its electronegativity rises. Example idea: carbon in sp hybridisation is more electronegative than carbon in sp3.
Ionization enthalpy and electron gain enthalpy are measured for a single free atom, so they have fixed experimental values. Electronegativity is not measurable directly and only exists inside a bond, so it has no single fixed number. That is why we use scales (Pauling, Mulliken, Allred-Rochow) that give approximate values, not exact ones.
The number in the table is an approximate or average value on a chosen scale (usually Pauling, where F = 4.0). It is a useful rough guide for comparing elements and predicting bond type. But for exact behaviour in a specific compound, the value can shift a little. For NEET, use the table values to compare, but know that the true value is not fixed.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
No. Unlike ionization enthalpy and electron gain enthalpy, electronegativity cannot be measured directly. We use scales such as Pauling, Mulliken-Jaffe and Allred-Rochow to give approximate values.
Yes. A higher oxidation state makes an atom pull shared electrons more strongly, so its effective electronegativity increases. This is one reason the value is not constant.
Fluorine is assigned 4.0 on the Pauling scale. It is the most electronegative element and is used as the reference point for the scale.
NTA sets statement-based questions where one option claims an electronegativity value is fixed or the same in all compounds. Knowing electronegativity is not constant lets you mark that statement false quickly.
