What Is Electronegativity and How Does It Affect Bond Polarity?
Electronegativity is an atom's ability to attract electrons toward itself in a covalent bond. This intrinsic property varies across the periodic table—fluorine is the most electronegative (3.98), and francium is the least (0.7). When two atoms with different electronegativities form a bond, the shared electrons spend more time near the more electronegative atom, creating a polar bond.
Electronegativity measures how strongly an atom pulls on shared electrons. Higher electronegativity difference between bonded atoms → more polar the bond. Bond polarity determines how the electron density is distributed.
Step-by-step worked examples
Compare electronegativity of C, N, and O. Which is highest?
C: 2.5, N: 3.0, O: 3.5 O > N > C Oxygen has highest electronegativity. Reason: rightward and upward in periodic table → more electronegative.
How does electronegativity affect the H–F bond?
H: 2.1, F: 3.98 → ΔEN = 1.88 Very large difference → highly polar bond. Electrons pulled strongly toward F → F is δ⁻, H is δ⁺.
Why is F more electronegative than Cl even though Cl is larger?
F is in period 2, Cl in period 3. F has higher nuclear charge relative to electron shielding. Smaller atomic radius + higher Z → electrons closer to nucleus → stronger pull. F (3.98) > Cl (3.0).
Flashcards
Quick quiz
Q1.Electronegativity increases as you move…
Q2.Which pair has the largest electronegativity difference?
Q3.Why is F–F nonpolar despite F being highly electronegative?
Q4.In the H–Cl bond, which atom is partially negative?
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Common mistakes
Electronegativity and atomic radius always increase together. — Correct: Atomic radius increases down the table; electronegativity decreases down, increases right.
A highly electronegative atom always makes polar bonds. — Correct: Two identical highly electronegative atoms (e.g., F–F) form nonpolar bonds.
Electronegativity is the same as ionization energy. — Correct: Ionization energy removes an electron; electronegativity attracts shared electrons.
Electronegativity is measured in standard units. — Correct: Common scale is Pauling (0.7–3.98), a relative scale with no units.
FAQ
What is the electronegativity of fluorine?
3.98 (on the Pauling scale), the highest of all elements.
How does atom size affect electronegativity?
Smaller atoms (right and up in the table) have higher electronegativity because electrons are closer to the nucleus and experience a stronger pull.
Why does electronegativity increase from left to right across a period?
Increasing nuclear charge pulls the electron cloud more strongly, while electron shielding stays roughly constant.
What is the relationship between electronegativity and bond polarity?
Larger electronegativity difference → stronger electron pull toward one atom → more polar the bond.