Start with the recap, study the fully worked examples, then use the practice problems to
check your understanding of Electronegativity.
This page combines explanation, solved examples, and follow-up practice so you can move
from recognition to confident problem-solving in Chemistry.
Concept Recap
A dimensionless measure of how strongly an atom attracts the shared electrons in a covalent bond toward itself, quantified on the Pauling scale from about 0.7 (cesium/francium) to 3.98 (fluorine).
How 'greedy' an atom is for electrons. Fluorine is most greedy.
Read the first worked example with the solution open so the structure is clear.
Try the practice problems before revealing each solution.
Use the related concepts and background knowledge badges if you feel stuck.
What to Focus On
Core idea:Electronegativity starts by identifying valence electrons, likely charges or sharing, and the structure that follows.
Common stuck point:Students often know a formula related to electronegativity but skip the recognition step: Am I explaining a substance by electron behavior, bond type, molecular shape, polarity, or attractions between particles? That leads to a correct-looking substitution attached to the wrong chemical model.
Sense of Study hint:Ask: Am I explaining a substance by electron behavior, bond type, molecular shape, polarity, or attractions between particles?
Worked Examples
Example 1
easy
Arrange the following elements in order of increasing electronegativity: Na, Cl, F, O.
Answer
Na<Cl<O<F
First step
1
Electronegativity increases across a period (left to right) and up a group (bottom to top).
Full solution
2
Na (Group 1, Period 3) is least electronegative. Cl (Group 17, Period 3) is more.
3
O (Group 16, Period 2) is higher still. F (Group 17, Period 2) is the most electronegative element.
4
Order: Na < Cl < O < F.
Electronegativity measures an atom's ability to attract shared electrons in a bond. Fluorine is the most electronegative element at 4.0 on the Pauling scale.
Example 2
medium
In the molecule HF, the electronegativity of H is 2.1 and F is 4.0. Describe the bond polarity and indicate the direction of the dipole.
Example 3
medium
Compute ΔEN for the C–Cl bond (C = 2.5, Cl = 3.0) and classify the bond.
Example 4
medium
In NH3, identify the bond polarity for each N–H bond and the direction of dipole.
Example 5
hard
Two atoms have EN 2.1 and 4.0. Estimate the % ionic character and classify the bond (rough rule: ΔEN=1.7⇒50% ionic).
Example 6
hard
Predict whether HBr or HI has a larger dipole moment, using EN values H 2.1, Br 2.8, I 2.5.
Example 7
challenge
Use ΔEN trends to predict whether water and oil would mix, given that water has polar O–H bonds while typical oil molecules are nonpolar C–H bonds.
Practice Problems
Try these problems on your own first, then open the solution to compare your method.
Example 1
easy
Which bond is more polar: H–Cl or H–Br? (EN values: H = 2.1, Cl = 3.0, Br = 2.8)
Example 2
medium
Which bond is more polar, C–H or O–H? Use these electronegativity values: C = 2.5, H = 2.1, O = 3.5.
Example 3
easy
Which element has the highest electronegativity on the Pauling scale?
Example 4
easy
Across a period (left to right), how does electronegativity generally change?
Example 5
easy
Down a group, how does electronegativity generally change?
Example 6
easy
Between Na and Cl, which atom is more electronegative?
Example 7
easy
Is electronegativity a measured quantity with units, or a dimensionless scale value?
Example 8
easy
Do noble gases like neon have high tabulated electronegativity values?
Example 9
easy
Which is more electronegative: oxygen or sulfur?
Example 10
easy
In a bond between H (2.1) and Cl (3.0), which atom carries the partial negative charge?
Example 11
medium
The electronegativity difference in H−F is 3.98−2.20. What is ΔEN?
Example 12
medium
Rank C, N, O by increasing electronegativity.
Example 13
medium
A bond has ΔEN=0.4. Classify it as nonpolar covalent, polar covalent, or ionic (cutoffs ~0.5 and ~1.7).
Example 14
medium
Which bond is more polar: O−H (ΔEN=1.24) or N−H (ΔEN=0.84)?
Example 15
medium
Why does fluorine have higher electronegativity than chlorine despite both being halogens?
Example 16
medium
Which atom in a C−O bond is partial negative, given C = 2.5 and O = 3.5?
Example 17
medium
Element X is in period 2 group 1; element Y is period 2 group 17. Which has greater electronegativity?
Example 18
medium
Order the bonds C−Cl, C−F, C−Br by increasing polarity (halogen EN: Cl 3.0, F 4.0, Br 2.8).
Example 19
medium
In CO, the bond's δ− end is on which atom (O = 3.5, C = 2.5)?
Example 20
challenge
Use Pauling's idea: a bond's ionic character grows with ΔEN. If ΔEN=1.7 gives roughly 50% ionic character, classify a Na−Cl bond with ΔEN=2.1.
Example 21
challenge
Two atoms A and B have identical electronegativities. What is ΔEN, and what bond type results?
Example 22
challenge
Explain why electronegativity does NOT increase smoothly down group 1 even though nuclear charge increases.
Example 23
easy
Which element is the most electronegative on the Pauling scale?
Example 24
easy
Down a group of the periodic table, how does electronegativity change?
Example 25
easy
Between Li and F (same period 2), which atom has higher electronegativity?
Example 26
easy
In an H–O bond (H = 2.1, O = 3.5), which atom carries the partial negative charge?
Example 27
easy
True or false: noble gases like helium and neon are usually given high tabulated Pauling electronegativities.
Example 28
medium
Which is more polar: H–F or H–Cl? Use EN values H = 2.1, F = 4.0, Cl = 3.0.
Example 29
medium
Rank the bonds C–H, N–H, O–H by increasing polarity (EN: H 2.1, C 2.5, N 3.0, O 3.5).
Example 30
medium
Why does Cs have one of the lowest electronegativities of all elements?
Example 31
medium
Classify the bond in KBr using EN values K = 0.8, Br = 2.8.
Example 32
medium
In an O=O double bond (oxygen gas, O2), what is ΔEN and the bond type?
Example 33
medium
Which has greater EN: O (period 2) or S (period 3), and why?
Example 34
hard
CO2 is a linear molecule with two polar C=O bonds. Why is the molecule nonpolar overall?
Example 35
hard
Rank the following bonds from most ionic to most covalent: Na–F, Mg–O, Si–Cl (EN: Na 0.9, F 4.0, Mg 1.2, O 3.5, Si 1.8, Cl 3.0).
Example 36
hard
A bond between two atoms has ΔEN=0.3. Predict whether the molecule containing only that bond would conduct electricity when melted.
Example 37
hard
Why is the diagonal relationship Li–Mg or Be–Al rooted partly in similar electronegativities?
Example 38
challenge
Explain why electron affinity and electronegativity are related but not the same concept.