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Lewis Dot Structure

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Electron Configurations

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Lewis Dot Structure


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You will explore Lewis dot structures, which are used to represent the valence electrons of atoms and show chemical bonding.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Explain that the outer electron shell is the most important in the chemical bonding process.
  • Explain the rules for drawing Lewis dot structures for single atoms.
  • Explain the rules for drawing Lewis dot structures for monatomic ions.
  • Explain the rules for drawing Lewis dot structures for simple molecules.
  • Compare the number of valence electrons for elements in the same group on the periodic table.

Everything You'll Have Covered

Gilbert Newton Lewis was an American chemist who created a notation to represent valence electrons, based on his work with chemical bonding. Lewis proposed that elements have similar chemical properties because of the similar number of electrons in their outer shells. These electrons, called "valence electrons," are critical to the bonding process. Valence electrons are either shared with other atoms to form covalent bonds or transferred to form ionic bonds.

Lewis noted that electron transfer or sharing usually occurs until an atom has a full complement of eight electrons in its outer shell. The noble gases have this full complement of electrons, and are relatively stable as a result. The only exception is helium, which has two valence electrons. All other atoms share or transfer electrons to become like the nearest noble gas. Eight electrons in an outer shell are called an octet, and the tendency to achieve an octet is known as the octet rule.

When drawing Lewis dot structures, begin by determining the total number of valence electrons. In Group IA on the periodic table, elements have one valence electron. In Group IIA, the elements have two valence electrons. This pattern continues through each group, ending with eight valence electrons for elements in Group VIIIA. Use dots to represent electrons, and then place electrons, one at a time, around the four sides (top, bottom, left, and right) of the element symbol. If each side of the symbol has one dot, and there are still electrons left, add dots in pairs until all electrons are used. For example, chlorine has seven valence electrons. Its Lewis dot structure can be built up like this:

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts Learners should be familiar with covalent bonding, ionic bonding, modern atomic model, and the periodic table.
Course Chemistry
Type of Tutorial Concept Development
Key Vocabulary atom, bond, bonding