Lewis Structures help us visualize how atoms share electrons in...
AP Chemistry78 views·Updated Jun 17, 2026·4 pagesUnderstanding Lewis Structures: Steps and Examples
1 / 4
1
of 4
Lewis Structures: The Basics
Lewis Structures are like molecular blueprints that show how valence electrons arrange themselves around atoms in covalently bonded molecules. They reveal which electrons are being shared between atoms and which ones remain as lone pairs. Remember though - these structures don't show the actual 3D shape of molecules!
In these diagrams, we represent single bonds with one line (sharing 2 electrons), double bonds with two lines (sharing 4 electrons), and triple bonds with three lines (sharing 6 electrons). For example, methane (CH₄) shows carbon with four single bonds to hydrogen atoms, while nitrogen gas (N₂) shows a triple bond between nitrogen atoms.
When drawing atoms, we can show lone pairs (unshared electrons) as dots. Sulfur might have dots representing its lone pairs, while oxygen in a double bond would share 4 electrons with another atom while keeping some electrons to itself.
Quick Tip: Valence electrons come from the outermost s and p orbitals, which is why most atoms can have up to 8 valence electrons (octet).
2
of 4
Drawing Lewis Structures: Rules and Steps
The famous Octet Rule tells us that atoms generally want 8 valence electrons to be stable (except hydrogen, which wants 2). When looking at a Lewis structure, check if each atom has access to 8 electrons either through sharing or as lone pairs.
To draw a Lewis Structure, first identify the central atom - usually it's the least electronegative atom, the one written first in the formula, or the "different" atom. For example, in NH₃, nitrogen is central while the hydrogens surround it.
Next, count the total available electrons by adding up all valence electrons from each atom. For NH₃, nitrogen contributes 5 electrons and each hydrogen contributes 1, giving a total of 8 valence electrons to work with.
Remember: The rules for Lewis Structures are more like guidelines than absolute rules. Some exceptions exist, especially for larger atoms!
3
of 4
Completing Lewis Structures
After counting available electrons, determine how many electrons each atom needs for a complete octet. For NH₃, nitrogen needs 8 electrons and each hydrogen needs 2, totaling 14 electrons needed.
Calculate how many bonds to draw by subtracting available electrons from needed electrons and dividing by 2. For NH₃: (14-8)/2 = 3 bonds. Draw these bonds connecting your atoms.
Finally, add lone pairs to any atoms that still need electrons to complete their octets. In NH₃, after drawing three N-H bonds, nitrogen still needs a lone pair to reach its octet.
Pro Tip: Always double-check your work by counting electrons in your final structure - the total should match what you calculated in step 3!
4
of 4
Special Cases and Formal Charge
Sometimes molecules break the octet rule, especially with larger atoms like sulfur (SF₆) or xenon (XeF₄). These atoms can access d orbitals, allowing them to accommodate more than 8 electrons.
Formal charge helps verify if your Lewis structure makes sense. Calculate it by subtracting the number of electrons "owned" by an atom from its normal valence electrons. Ideally, formal charges should be zero or as close to zero as possible.
When drawing multiple possible structures, choose the one where formal charges are minimized and distributed evenly. It's better to have two -1 charges than one -2 charge in your structure.
Important: When working with polyatomic ions like CO₃²⁻, remember to add or subtract electrons based on the overall charge of the molecule!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar Content
Most popular content: Lewis Structures
1Most popular content in AP Chemistry
9I
AP ChemistryIntroduction to Elemental Composition
Practice fundamental concepts of mass percentage and the law of definite proportions to determine the relative mass of elements in a pure substance.
9th7160
I
AP ChemistryIntroduction to Electron Configuration
Practice identifying ground-state electron configurations using the Aufbau principle, Hund's rule, and the Pauli exclusion principle.
9th3800
I
AP ChemistryIntroduction to Moles and Avogadro's Number
Practice converting between mass, moles, and number of particles using Avogadro's constant and the fundamental concept of the mole.
9th1820
AP Chemistryunits 1-9 ap chem
dives pretty deeply into each unit of the ap chem curriculum
10th3197
AP ChemistryReversible Reactions, Chemical Equilibrium, and Equilibrium Constants
Understanding the dynamic nature of reversible reactions and the concept of chemical equilibrium, as well as calculating the equilibrium constant for reactions.
9th621
AP ChemistryIntegrated Rate Law, Reaction Mechanisms, and Multistep Energy Diagrams
Introduction to integrated rate law, formulas for finding orders, example of half-life, steps for reaction completion, how to find rate determining step, identifying parts of a multistep energy diagram
739
AP ChemistryStoichiometry notes
Understand how to solve stoichiometry problems.
10th531
AP ChemistryIntroduction to Analytical Chemistry
This study note contains information on the basics of Analytical Chemistry, its applications, and minor concepts with examples.
650
AP ChemistryWhat is chemistry?
Covers matter, mass, weight, and the classification of matter.
12th490
Most popular content
9O
AP US HistoryOrigins and Dynamics of the Columbian Exchange
Analyze the ecological and economic motivations behind the initial transfer of goods, people, and diseases between the Old and New Worlds.
9th3,1280
I
AP US HistoryIntroduction to Early Cultural Interactions
Analyze the initial social and religious encounters between Europeans, Africans, and Indigenous peoples in the colonial Americas.
9th2,7730
O
AP World HistoryOrigins of Ancient River Civilizations
Analyze the environmental factors and technological innovations that led to the rise of early states in Mesopotamia, Egypt, and the Indus Valley.
9th3,1870
M
AP US HistoryMotivations for European Exploration
Analyze the economic, religious, and political factors that drove European powers to the Americas during the 15th and 16th centuries.
9th1,7780
F
AP PsychologyFoundations of Ethical Guidelines in Research
Practice the core principles of the APA ethical code including informed consent, debriefing, and the role of Institutional Review Boards.
9th1,3360
I
AP US HistoryIntroduction to Native American Societies
Examine the diverse social, political, and economic structures of North American indigenous groups prior to European contact.
9th1,1100
I
AP BiologyIntroduction to Biological Elements of Life
Practice identifying the essential elements including carbon, nitrogen, phosphorus, and sulfur that compose biological macromolecules.
9th1,7390
I
AP US HistoryIntroduction to the Spanish Encomienda System
Explore the fundamental economic and social structures of the Spanish colonial system, focusing on the encomienda and the casta social hierarchy.
9th8890
O
AP World HistoryOrigins and Continuity of the Byzantine Empire
Analyze the political and cultural transitions from the Roman Empire to the Byzantine Empire, focusing on the reign of Justinian I and his code.
9th1,6320
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user
AP Chemistry78 views·Updated Jun 17, 2026·4 pagesUnderstanding Lewis Structures: Steps and Examples
Lewis Structures help us visualize how atoms share electrons in molecules. They show us how valence electrons are arranged and how atoms connect to each other through chemical bonds, giving us a paper representation of covalent bonding.
1
of 4
Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Lewis Structures: The Basics
Lewis Structures are like molecular blueprints that show how valence electrons arrange themselves around atoms in covalently bonded molecules. They reveal which electrons are being shared between atoms and which ones remain as lone pairs. Remember though - these structures don't show the actual 3D shape of molecules!
In these diagrams, we represent single bonds with one line (sharing 2 electrons), double bonds with two lines (sharing 4 electrons), and triple bonds with three lines (sharing 6 electrons). For example, methane (CH₄) shows carbon with four single bonds to hydrogen atoms, while nitrogen gas (N₂) shows a triple bond between nitrogen atoms.
When drawing atoms, we can show lone pairs (unshared electrons) as dots. Sulfur might have dots representing its lone pairs, while oxygen in a double bond would share 4 electrons with another atom while keeping some electrons to itself.
Quick Tip: Valence electrons come from the outermost s and p orbitals, which is why most atoms can have up to 8 valence electrons (octet).
2
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Drawing Lewis Structures: Rules and Steps
The famous Octet Rule tells us that atoms generally want 8 valence electrons to be stable (except hydrogen, which wants 2). When looking at a Lewis structure, check if each atom has access to 8 electrons either through sharing or as lone pairs.
To draw a Lewis Structure, first identify the central atom - usually it's the least electronegative atom, the one written first in the formula, or the "different" atom. For example, in NH₃, nitrogen is central while the hydrogens surround it.
Next, count the total available electrons by adding up all valence electrons from each atom. For NH₃, nitrogen contributes 5 electrons and each hydrogen contributes 1, giving a total of 8 valence electrons to work with.
Remember: The rules for Lewis Structures are more like guidelines than absolute rules. Some exceptions exist, especially for larger atoms!
3
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Completing Lewis Structures
After counting available electrons, determine how many electrons each atom needs for a complete octet. For NH₃, nitrogen needs 8 electrons and each hydrogen needs 2, totaling 14 electrons needed.
Calculate how many bonds to draw by subtracting available electrons from needed electrons and dividing by 2. For NH₃: (14-8)/2 = 3 bonds. Draw these bonds connecting your atoms.
Finally, add lone pairs to any atoms that still need electrons to complete their octets. In NH₃, after drawing three N-H bonds, nitrogen still needs a lone pair to reach its octet.
Pro Tip: Always double-check your work by counting electrons in your final structure - the total should match what you calculated in step 3!
4
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Special Cases and Formal Charge
Sometimes molecules break the octet rule, especially with larger atoms like sulfur (SF₆) or xenon (XeF₄). These atoms can access d orbitals, allowing them to accommodate more than 8 electrons.
Formal charge helps verify if your Lewis structure makes sense. Calculate it by subtracting the number of electrons "owned" by an atom from its normal valence electrons. Ideally, formal charges should be zero or as close to zero as possible.
When drawing multiple possible structures, choose the one where formal charges are minimized and distributed evenly. It's better to have two -1 charges than one -2 charge in your structure.
Important: When working with polyatomic ions like CO₃²⁻, remember to add or subtract electrons based on the overall charge of the molecule!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar Content
Most popular content: Lewis Structures
1Most popular content in AP Chemistry
9I
AP ChemistryIntroduction to Elemental Composition
Practice fundamental concepts of mass percentage and the law of definite proportions to determine the relative mass of elements in a pure substance.
9th7160
I
AP ChemistryIntroduction to Electron Configuration
Practice identifying ground-state electron configurations using the Aufbau principle, Hund's rule, and the Pauli exclusion principle.
9th3800
I
AP ChemistryIntroduction to Moles and Avogadro's Number
Practice converting between mass, moles, and number of particles using Avogadro's constant and the fundamental concept of the mole.
9th1820
AP Chemistryunits 1-9 ap chem
dives pretty deeply into each unit of the ap chem curriculum
10th3197
AP ChemistryReversible Reactions, Chemical Equilibrium, and Equilibrium Constants
Understanding the dynamic nature of reversible reactions and the concept of chemical equilibrium, as well as calculating the equilibrium constant for reactions.
9th621
AP ChemistryIntegrated Rate Law, Reaction Mechanisms, and Multistep Energy Diagrams
Introduction to integrated rate law, formulas for finding orders, example of half-life, steps for reaction completion, how to find rate determining step, identifying parts of a multistep energy diagram
739
AP ChemistryStoichiometry notes
Understand how to solve stoichiometry problems.
10th531
AP ChemistryIntroduction to Analytical Chemistry
This study note contains information on the basics of Analytical Chemistry, its applications, and minor concepts with examples.
650
AP ChemistryWhat is chemistry?
Covers matter, mass, weight, and the classification of matter.
12th490
Most popular content
9O
AP US HistoryOrigins and Dynamics of the Columbian Exchange
Analyze the ecological and economic motivations behind the initial transfer of goods, people, and diseases between the Old and New Worlds.
9th3,1280
I
AP US HistoryIntroduction to Early Cultural Interactions
Analyze the initial social and religious encounters between Europeans, Africans, and Indigenous peoples in the colonial Americas.
9th2,7730
O
AP World HistoryOrigins of Ancient River Civilizations
Analyze the environmental factors and technological innovations that led to the rise of early states in Mesopotamia, Egypt, and the Indus Valley.
9th3,1870
M
AP US HistoryMotivations for European Exploration
Analyze the economic, religious, and political factors that drove European powers to the Americas during the 15th and 16th centuries.
9th1,7780
F
AP PsychologyFoundations of Ethical Guidelines in Research
Practice the core principles of the APA ethical code including informed consent, debriefing, and the role of Institutional Review Boards.
9th1,3360
I
AP US HistoryIntroduction to Native American Societies
Examine the diverse social, political, and economic structures of North American indigenous groups prior to European contact.
9th1,1100
I
AP BiologyIntroduction to Biological Elements of Life
Practice identifying the essential elements including carbon, nitrogen, phosphorus, and sulfur that compose biological macromolecules.
9th1,7390
I
AP US HistoryIntroduction to the Spanish Encomienda System
Explore the fundamental economic and social structures of the Spanish colonial system, focusing on the encomienda and the casta social hierarchy.
9th8890
O
AP World HistoryOrigins and Continuity of the Byzantine Empire
Analyze the political and cultural transitions from the Roman Empire to the Byzantine Empire, focusing on the reign of Justinian I and his code.
9th1,6320
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user