Foundation reading 2 of 17 · ~6 min
Count outer electrons
Your goal: Use main-group numbers to count valence electrons and read Lewis symbols.
A focused reading from Valence Electrons and the Octet Rule. Reading time is a Chem Help estimate.
Optional prerequisite review
Review if useful. These suggestions never lock a step.
What counts as a valence electron
Valence electrons are the electrons in the highest occupied principal energy level. For main-group elements the group number gives the count directly: group 1 has 1, group 2 has 2, group 13 has 3, and so on up to group 18 with 8.
Sulfur is in group 16, so it has 6 valence electrons regardless of which period it sits in.
Lewis symbols
A Lewis symbol is the element symbol surrounded by one dot per valence electron.
Dots are placed singly on the four sides first and then paired up, which is why nitrogen shows three single dots plus one pair and oxygen shows two single dots plus two pairs. Those unpaired dots are the electrons available for bonding.
Sources and further reading
- Chemistry 2e, Section 7.3: Lewis Symbols and StructuresOpenStax · Rice University · 7.3View source
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The current online Chemistry 2e edition lists CC BY-NC-SA 4.0. The source version used for this lesson and its applicable rights remain unverified.
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