Lewis Structure Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Lewis Structure.

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 two-dimensional diagram that represents the arrangement of valence electrons around atoms in a molecule, showing bonding pairs as lines between atoms and non-bonding (lone) pairs as dots.

A map showing how electrons are arranged and shared between atoms.

Read the full concept explanation →

How to Use These Examples

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: Lewis Structure starts by identifying valence electrons, likely charges or sharing, and the structure that follows.

Common stuck point: Students often know a formula related to lewis structure 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

Draw the Lewis structure for water (

\text{H}_2\text{O}

H₂O: 2 lone pairs on oxygen give water its bent shape

Answer

\text{H–O–H with 2 lone pairs on O}

First step

Count total valence electrons: O has 6, each H has 1. Total =

6 + 2(1) = 8

Full solution

2
Place O as the central atom with single bonds to each H (uses 4 electrons).
3
Distribute remaining 4 electrons as 2 lone pairs on oxygen.
4
Check: O has 4 bonding + 4 lone pair = 8 electrons (octet satisfied). Each H has 2 electrons (duet satisfied).

Lewis structures show the arrangement of valence electrons in a molecule. Oxygen's two lone pairs and two bonding pairs create the bent shape of water.

Example 2

medium

Draw the Lewis structure for carbon dioxide (

\text{CO}_2

Example 3

medium

Draw the Lewis structure for

\text{HCN}

and state the bond order of the C–N bond.

H–C≡N: linear structure — what is the bond order of the C–N bond?

Example 4

medium

Draw a Lewis structure for

\text{N}_2

and identify the bond order.

Example 5

medium

Draw a Lewis structure for

\text{CH}_2\text{O}

(formaldehyde) and identify the type of C–O bond.

H₂C=O: carbon forms 2 C–H bonds and 1 C–O bond — what type is the C–O bond?

Example 6

hard

Compute the formal charge on the central sulfur atom in

\text{SO}_4^{2-}

assuming the conventional Lewis structure with two S=O double bonds and two S–O single bonds.

Example 7

hard

Draw the Lewis structure for

\text{O}_3

(ozone) and explain why two resonance structures are needed.

O₃: one resonance structure — why are two resonance structures needed?

Example 8

hard

Determine the formal charge on each atom in the Lewis structure of carbon monoxide,

:\!\text{C}\!\equiv\!\text{O}\!:

Example 9

challenge

The thiocyanate ion

\text{SCN}^-

has three plausible Lewis structures. Use formal charges to identify the most likely structure (atom skeleton S–C–N).

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

hard

Draw the Lewis structure for the nitrate ion (

\text{NO}_3^-

). Include formal charges.

NO₃⁻: trigonal planar, one resonance structure shown (N formal charge +1)

Example 2

medium

Draw the Lewis structure for ammonia (

\text{NH}_3

), and state how many lone pairs are on the nitrogen atom.

NH₃: three N–H bonds, 1 lone pair on nitrogen

Example 3

easy

How many valence electrons does a single oxygen atom (group 16) have?

Example 4

easy

What is the total number of valence electrons in a water molecule

H_2O

Example 5

easy

How many bonding pairs are shown by a single line in a Lewis structure?

Example 6

easy

How many valence electrons does nitrogen (group 15) contribute to a Lewis structure?

Example 7

easy

In a completed Lewis structure, how many electrons satisfy the octet of a non-hydrogen atom?

Example 8

easy

How many lone pairs are on the oxygen atom in a water

H_2O

Lewis structure?

H₂O: oxygen has 6 valence electrons; after 2 bonds, how many lone pairs remain?

Example 9

easy

How many valence electrons does carbon (group 14) bring to a Lewis structure?

Example 10

easy

For the ion

OH^-

, how many total valence electrons should the Lewis structure show?

Example 11

medium

Draw and count: how many bonds (single-bond equivalents) connect the atoms in

CO_2

O=C=O: how many bonding pairs (bond-pair equivalents) connect the atoms?

Example 12

medium

How many lone pairs are on the central nitrogen in ammonia

NH_3

NH₃: nitrogen forms 3 bonds — how many lone pairs remain on N?

Example 13

medium

In the nitrate ion

NO_3^-

, how many total valence electrons does its Lewis structure contain?

Example 14

medium

How many bonding electrons are in the triple bond of

N_2

Example 15

medium

For

CH_4

, verify carbon's octet: how many electrons surround carbon in the Lewis structure?

CH₄: four C–H bonds — how many electrons surround carbon?

Example 16

medium

How many lone pairs total are in the Lewis structure of

F_2

Example 17

medium

CO_2

, how many lone pairs are on EACH oxygen atom?

Example 18

medium

How many total valence electrons are in the ammonium ion

NH_4^+

NH₄⁺: four N–H bonds, no lone pairs — how many total valence electrons?

Example 19

medium

How many bonding pairs surround the carbon in formaldehyde

CH_2O

(structure H-C(=O)-H)?

CH₂O: two C–H bonds and one C=O double bond — how many bonding pairs total?

Example 20

challenge

Determine the formal charge on the central oxygen in ozone

O_3

(bent, one O=O and one O-O, central O has one lone pair).

O₃: central O has 1 lone pair, one double bond, one single bond — what is its formal charge?

Example 21

challenge

Sulfur in

SF_6

exceeds the octet. How many electrons surround the sulfur atom?

SF₆: six S–F bonds — how many electrons surround the sulfur?

Example 22

challenge

In the carbonate ion

CO_3^{2-}

, how many equivalent resonance structures place the single C=O double bond?

Example 23

easy

How many valence electrons does fluorine (group 17) bring to a Lewis structure?

Example 24

easy

In a Lewis structure for

\text{CH}_4

, how many bonding pairs surround carbon?

Example 25

easy

How many lone pairs does the nitrogen atom have in

\text{NH}_3

NH₃: three bonds to H — how many lone pairs on nitrogen?

Example 26

easy

How many valence electrons total are in a Lewis structure for

\text{NH}_3

Example 27

easy

How many valence electrons does the polyatomic ion

\text{NH}_4^+

have to distribute?

Example 28

medium

How many lone pairs are on each oxygen atom in the Lewis structure of

\text{CO}_2

Example 29

medium

Calculate the formal charge on nitrogen in the Lewis structure of

\text{NH}_3

Example 30

medium

How many total valence electrons are needed to draw the Lewis structure of

\text{CO}_3^{2-}

Example 31

medium

How many lone pairs surround the central atom in

\text{H}_2\text{S}

H₂S: sulfur mirrors oxygen in water — how many lone pairs on S?

Example 32

medium

How many bonding pairs are around each carbon in ethene,

\text{C}_2\text{H}_4

Example 33

hard

How many resonance structures does the nitrate ion

\text{NO}_3^-

have, equivalent by symmetry?

Example 34

hard

What is the bond order in

\text{O}_3

between the central O and either outer O?

Example 35

hard

How many valence electrons total are in the Lewis structure of sulfate

\text{SO}_4^{2-}

← Back to Lewis Structure Practice Mode

Related Concepts

Covalent Bond Octet Rule Molecular Geometry Molecular Polarity

Background Knowledge

These ideas may be useful before you work through the harder examples.

covalent bondoctet rule