How many valence electrons are in an atom of phosphorus? a. 2 b. 3 c. 4 d. 5
The number of valance electrons any atom has can be found by looking at the group number at the top of the column the atom is in. [ Except for the transition metals (groups 3-12), single digit groups give the valence electrons, for double digit group numbers (groups 13-18), take the second of the two digits as the number of valence electrons. The transition elements usually have 2 but some
in groups 6 and 11 have only 1.
So as the first responder noted, phosphorus in group 15 on the periodic table (a two digit group number) has 5 valence electrons.
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