How do the valence electrons change as you go across a period?
Valence electrons are the electrons in the highest energy level or outer shell and increase in number as you go left to right for the representative elements. However, the transition metals usually have one or two valence electrons.
Elements in Alkali Metals Group I (column) Lithium, Sodim and Potassium all have one valence electron. The Alkali Earth Metals Group II Magnesium, Calcium all have two valence electrons. Group 13 elements Boron and Aluminum have three valence this electrons. This pattern continues across the periods until th Halogens Group 17 Florine an Chlorine have seven valence electrons and finally the Noble Gases Group 18 Neon and Argon have eight valence and full s and p orbitals completing he rule of octet.
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