Chemistry · Periodic Classification Of Properties · NEET
Linus Pauling, an American scientist, did this in 1922. He CHOSE the number 4.0 by himself (arbitrarily) because fluorine pulls shared electrons the strongest of all elements. There is no deep formula behind the 4.0 itself; it is just a fixed reference point. Every other element gets a smaller value by comparing its bond energies to fluorine. For NEET, remember: F = 4.0 is the TOP of the Pauling scale.
No. NCERT states it clearly: unlike ionization enthalpy and electron gain enthalpy, electronegativity is NOT directly measurable. It is only a qualitative (comparing) measure of how well an atom in a compound attracts shared electrons. So the Pauling scale gives numbers, but these numbers have NO units. This is a favourite NEET trap: electronegativity has no unit.
No, they are close but NOT equal. On the Pauling scale nitrogen is about 3.0 and chlorine is about 3.16 (usually written near 3.0). Many students wrongly think they are identical because both are near 3. NEET 2025 tested exactly this: the statement 'N and Cl have the same electronegativity' is treated carefully, so do not assume equal. They are different values.
Fluorine (F = 4.0) is the MOST electronegative element on the Pauling scale. After it come oxygen (about 3.5), then nitrogen and chlorine (about 3.0). The least electronegative are the large metals at the bottom-left, like caesium (Cs) and francium (about 0.7). So the scale runs roughly from 0.7 (Cs) up to 4.0 (F).
Across a period (left to right) electronegativity INCREASES, because effective nuclear charge rises and atomic size shrinks, so the nucleus pulls shared electrons harder. Down a group (top to bottom) it DECREASES, because the atom gets bigger and the outer electrons are farther from the nucleus. This is why F (top-right, small) is highest and Cs (bottom-left, large) is lowest.
NCERT names three scales: Pauling, Mulliken-Jaffe, and Allred-Rochow. The Pauling scale is the most widely used because it was the first practical scale, it is simple, and its values match chemical behaviour well. For NEET you mainly need the Pauling values and trends; the other scales are just names to recognise (see the next concept).
Arrange the following elements in increasing order of electronegativity: N, O, F, C, Si.
Which statements are true? (B) On the Pauling scale, the electronegativity values of N and Cl are not the same. (C) Ar, K+, Cl-, Ca2+, S2- are isoelectronic. (E) The atomic radius of Cs is greater than Li and Rb.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Fluorine is fixed at 4.0, the highest value on the Pauling scale. It is the most electronegative element.
No. Electronegativity is not directly measurable, so its values (including on the Pauling scale) have no units.
Linus Pauling, an American scientist, proposed it in 1922. He assigned the value 4.0 to fluorine as the reference.
Three: the Pauling scale, the Mulliken-Jaffe scale, and the Allred-Rochow scale. The Pauling scale is the most widely used.
Because effective nuclear charge increases and atomic size decreases, so the nucleus pulls the shared bonding electrons more strongly.
