Electrons in the outermost shell that take part in bonding and determine chemical behaviour.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
Valence electrons are the electrons in the outermost shell of an atom, and they take part in chemical bonding and determine chemical behaviour. For main-group elements the units digit of the group number gives the number of valence electrons, so group 1 has one and group 17 has seven. Lewis structures show only valence electrons as dots around each atom. The number of valence electrons predicts how many bonds an atom can form and its typical oxidation states. Transition metals have more complicated valence sets that include d electrons.
Key ideas: Valence electrons are those in the outermost shell (highest n), plus d electrons for transition metals when bonding. For main groups: group 1 has 1, group 2 has 2, group 13 to 18 have group number minus 10. They are shown in Lewis dot symbols, and the octet rule (8 electrons) guides bonding.
Common mistakes and connections: Students count the whole configuration, or include inner d and f electrons for main-group elements, for example gallium has 3 valence electrons not 13. Helium has 2 but is in group 18. Valence electron count predicts charge of ions, bond number and the Lewis structures.
Across period 3 the number of valence electrons rises from 1 for sodium to 8 for argon, which fixes each element's bonding behaviour. The interactive lesson shows this as a live animation or chart.
Sulfur, in group 16, has 6 valence electrons and typically forms two bonds in compounds such as H2S.
Electrons in the outermost shell that take part in bonding and determine chemical behaviour.
Valence Electrons is a beginner topic in Atomic Structure & Periodicity. It needs no earlier chemistry lessons and is a good starting point.
Study these earlier topics in Atomic Structure & Periodicity first: Electron Configuration, Noble Gas Shorthand, Exceptional Configurations of Cr and Cu.
The next topics in Atomic Structure & Periodicity are Core Electrons and Effective Nuclear Charge.
Yes. The interactive lesson includes a self-check question on Valence Electrons, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Valence Electrons is topic 68 of 115 in Atomic Structure & Periodicity.