Here is a summary of the number of valence electrons for each group in the periodic table:
Group 1 (Alkali metals): 1 valence electron Group 2 (Alkaline earth metals): 2 valence electrons Group 13: 3 valence electrons Group 14: 4 valence electrons Group 15: 5 valence electrons Group 16: 6 valence electrons Group 17 (Halogens): 7 valence electrons Group 18 (Noble gases): 8 valence electrons (except for helium with 2 valence electrons)
In general, the group number of an element indicates the number of valence electrons it has, with the exception of the transition metals, which have more complex electron configurations. The valence electrons are the electrons in the outermost energy level (shell) of an atom and are primarily involved in chemical bonding and reactions.