Finding the Number of Valence Electrons for an Element
An explanation and practice for finding the number of valence electrons for elements on the periodic table. This is a key first step for drawing Lewis dot structures for molecules.
Looking at the Periodic Table, atoms have a regularly occurring number of valence electrons based on their Group number.
Group 1: One Valence Electron
Group 2: Two Valence Electrons
Group 13 (also called 3A): Three Valence Electrons
Group 14 (also called 4A): Four Valence Electrons
Group 15 (also called 5A): Five Valence Electrons
Group 16 (also called 6A): Six Valence Electrons
Group 17 (also called 7A): Seven Valence Electrons
Group 18 (also called 8A): Eight Valence Electrons*
* Although in Group 18, the element Helium only has two valence electrons.
In general we do not draw Lewis Structures for atoms of the Transition Metals (Groups 3-12).
Get more chemistry help at www.Breslyn.org.