Start with the recap, study the fully worked examples, then use the practice problems to
check your understanding of Covalent Bond.
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 chemical bond formed when two atoms share one or more pairs of valence electrons, creating a strong attractive force that holds them together as a molecule.
Atoms hold electrons together like kids sharing a toy. Neither gives it away.
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:Covalent Bond starts by identifying valence electrons, likely charges or sharing, and the structure that follows.
Common stuck point:Students often know a formula related to covalent bond 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
How does a covalent bond form in a hydrogen molecule (H2)?
Answer
H:H or H–H (single covalent bond)
First step
1
Each hydrogen atom has 1 valence electron and needs 1 more to fill its 1s shell.
Full solution
2
Two H atoms share their electrons, forming a single covalent bond: H–H.
3
Each atom now effectively has 2 electrons, achieving the helium configuration.
Covalent bonds form when nonmetal atoms share electrons to achieve stable electron configurations. The shared pair is attracted to both nuclei, holding the atoms together.
Example 2
medium
Distinguish between single, double, and triple covalent bonds. Give an example of each.
Example 3
medium
Draw the dot structure (count electrons) for H2O and state the number of lone pairs on oxygen.H₂O: how many lone pairs are on oxygen?
Example 4
medium
Compare the bond strengths of single, double, and triple C-C bonds (in general terms).
Example 5
medium
A substance melts at −78∘C and does not conduct electricity in any state. What bond type is most likely?
Example 6
hard
Phosphorus pentachloride PCl5 exists despite phosphorus apparently exceeding the octet. How many bonds does P form, and what does this imply?PCl₅: how many bonds does phosphorus form, and what does this imply?
Practice Problems
Try these problems on your own first, then open the solution to compare your method.
Example 1
easy
How many covalent bonds does carbon typically form? Explain why.
Example 2
medium
In a chlorine molecule (Cl2), how many electrons are shared, and why does sharing help each chlorine atom?
Example 3
easy
In a covalent bond, are electrons shared or transferred?
Example 4
easy
How many electrons are in one single covalent bond?
Example 5
easy
Which pair forms a covalent bond: two oxygen atoms, or sodium and fluorine?
Example 6
easy
How many electrons are shared in a double bond?
Example 7
easy
Do covalent compounds typically form molecules or extended ionic lattices?
Example 8
easy
How many covalent bonds does carbon typically form?CH₄: how many covalent bonds does carbon form?
Example 9
easy
In water, how does each O-H covalent bond help oxygen and hydrogen?
Example 10
easy
Is the bond in Cl2 ionic or covalent?
Example 11
medium
Nitrogen gas is N2 with a triple bond. How many electrons are shared, and why is N2 so stable?
Example 12
medium
Why can a covalent bond like the triple bond in N2 be stronger than many ionic bonds?
Example 13
medium
Distinguish a polar covalent bond from a nonpolar covalent bond using H-Cl versus Cl-Cl.
Example 14
medium
How many covalent bonds does oxygen (6 valence electrons) typically form, and how does that give water its formula?
Example 15
medium
Why do covalent molecular substances often have low melting points compared to ionic compounds?
Example 16
medium
In carbon dioxide CO2, carbon double-bonds to two oxygens. How many shared electrons total, and is carbon's octet satisfied?CO₂: count the total shared electrons across both C=O bonds
Example 17
medium
Why is H2 held by a covalent bond rather than an ionic bond?
Example 18
medium
How many covalent bonds does fluorine (7 valence electrons) typically form, and what molecule does F2 illustrate?
Example 19
medium
Why do covalent molecular substances like sugar not conduct electricity, even when melted?
Example 20
challenge
Determine the number of bonds and lone pairs on nitrogen in ammonia NH3, given nitrogen has 5 valence electrons.NH₃: identify the number of bonds and lone pairs on nitrogen
Example 21
challenge
Methane CH4 and water H2O are both covalent. Explain why carbon forms 4 bonds but oxygen forms only 2.
Example 22
challenge
A substance has a low melting point, does not conduct electricity even when molten, and exists as discrete units. Identify the bond type and justify each clue.
Example 23
easy
Which atoms typically form covalent bonds: two nonmetals, or a metal with a nonmetal?
Example 24
easy
How many electrons does hydrogen need to share to complete its outer shell?
Example 25
easy
Identify the bond type in HF: ionic or covalent?
Example 26
easy
In O2, how many electrons total are shared between the two oxygen atoms?
Example 27
easy
Do covalent compounds typically conduct electricity when dissolved in water?
Example 28
medium
Predict whether C2H4 (ethylene) contains a single, double, or triple C-C bond.C₂H₄: is the C-C bond single, double, or triple?
Example 29
medium
Which is more polar: the H-F bond or the H-Cl bond?
Example 30
medium
In CH4, how many shared electron pairs surround the central carbon?CH₄: how many shared electron pairs surround the central carbon?
Example 31
medium
Why is N2 used as an inert atmosphere despite nitrogen being abundant in living systems?
Example 32
medium
How many bonds does sulfur typically form in H2S?H₂S: how many covalent bonds does sulfur form here?
Example 33
medium
In HCN, what is the bond order between C and N?HCN: what is the bond order between carbon and nitrogen?
Example 34
medium
A coordinate (dative) covalent bond differs from a normal covalent bond because:
Example 35
hard
In SO2, the central sulfur has one double bond and one single bond (with resonance). How many total bond pairs and lone pairs are around S?
Example 36
hard
Why is diamond, a covalent network solid, extremely hard with a very high melting point (~3550 °C)?
Example 37
hard
Use electronegativity differences to classify the C-H bond: nonpolar covalent, polar covalent, or ionic? (EN: C = 2.55, H = 2.20)
Example 38
hard
Compare bond lengths: C-C, C=C, and C≡C. Order from longest to shortest.
Example 39
hard
A 0.50 mol sample of N2 is completely dissociated into atoms. Using bond energy 945 kJ/mol, find the energy required.
Example 40
challenge
In O3 (ozone), the central O has formal bonds drawn as one single and one double bond. What is the average bond order between the central O and each terminal O?
Example 41
challenge
Using approximate bond energies (H-H = 436, Cl-Cl = 243, H-Cl = 431 kJ/mol), estimate ΔH for H2+Cl2→2HCl.