Lewis structure
Diagrams showing bonding and lone pairs in molecules.
Lewis structures – also called Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDs) – are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist in the molecule. Introduced by Gilbert N. Lewis in his 1916 article The Atom and the Molecule, a Lewis structure can be drawn for any covalently bonded molecule, as well as coordination compounds. Lewis structures extend the concept of the electron dot diagram by adding lines between atoms to represent shared pairs in a chemical bond.
- introduced_by
- Gilbert N. Lewis
- year_introduced
- 1916
- field
- Chemistry
- known_for
- Diagrams showing bonding and lone pairs in molecules
- applies_to
- Covalently bonded molecules and coordination compounds
Lore & Background
Lewis structures show each atom and its position in the structure of the molecule using its chemical symbol. Lines are drawn between atoms that are bonded to one another (pairs of dots can be used instead of lines). Excess electrons that form lone pairs are represented as pairs of dots, and are placed next to the atoms. Although main group elements of the second period and beyond usually react by gaining, losing, or sharing electrons until they have achieved a valence shell electron configuration with a full octet of (8) electrons, hydrogen instead obeys the duplet rule, forming one bond for a complete valence shell of two electrons. For a neutral molecule, the total number of electrons represented in a Lewis structure is equal to the sum of the numbers of valence electrons on each individual atom, not the maximum possible. Non-valence electrons are not represented in Lewis structures as they do not bond. A stepwise construction method is used: initially, one line (representing a single bond) is drawn between each pair of connected atoms; then remaining electrons are placed as dots, first to outer atoms; finally, lone pairs may be converted to bonding pairs to satisfy octets. For polyatomic ions, extra electrons are added for negative ions and fewer for positive ions, and the entire structure is placed in brackets with the charge as a superscript.
Reader's Guide
Lewis structures are fundamental tools in chemistry for visualizing the arrangement of valence electrons in molecules and ions. They allow chemists to predict bonding patterns, identify lone pairs, and assess molecular stability. The concept of formal charge, derived from Lewis structures, helps in comparing possible resonance structures by calculating the apparent electronic charge of each atom assuming exclusive covalency. For molecules with multiple valid bonding arrangements, resonance structures are written with double-headed arrows between them, representing the molecule as a hybrid of these forms. The nitrate ion (NO−3) is a classic example, with three equivalent resonance structures. Lewis structures also underpin the octet rule and its exceptions, such as hypervalent molecules like sulfur hexafluoride, where single bonds can be moved to create resonance structures. Despite their simplicity, Lewis structures remain essential for teaching chemical bonding and for initial analysis of reaction mechanisms.
Did You Know?
- Lewis structures were introduced by Gilbert N. Lewis in his 1916 article The Atom and the Molecule.
- Hydrogen obeys the duplet rule, forming one bond for a complete valence shell of two electrons.
- For polyatomic ions, the entire Lewis structure is placed in brackets with the charge written as a superscript on the upper right.
- The nitrate ion (NO−3) has three possible resonance structures because it is symmetrical.
Frequently Asked Questions
Who is Lewis structure?
Lewis structure is a diagramming convention introduced by Gilbert N. Lewis in his 1916 paper on atoms and molecules. It serves as a visual shorthand for how atoms connect within a molecule and where any unshared electrons reside.
What are Lewis structure's powers and role?
Its core ability is to map shared electron pairs between atoms using lines while also flagging lone pairs that do not participate in bonding. It applies to any covalently bonded molecule and extends into coordination compounds as well.
How does Lewis structure's story end?
Because it is a permanent tool in the chemist's toolkit rather than a narrative arc, it has no plot-ending. Its lasting legacy is that it remains a foundational way for students and researchers to visualize molecular connectivity and electron distribution to this day.
Why is Lewis structure important?
It builds on the simpler electron dot diagram by adding bond lines, giving chemists a quick, intuitive picture of molecular connectivity without needing advanced quantum notation. That makes it an indispensable first step in reasoning about reactivity, polarity, and molecular shape.
What other names does Lewis structure go by?
Textbooks and fans use several aliases, including Lewis dot formula, Lewis dot structure, electron dot structure, and Lewis electron dot structure (sometimes abbreviated LED). All of these refer to the same diagramming convention Lewis published in 1916.
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