Valence shortcut: group 13 has {{c1::3}}, 14 has {{c2::4}}, 15 has {{c3::5}}, 16 has {{c4::6}}, 17 has {{c5::7}}, 18 has {{c6::8}} (He is 2).
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Valence shortcut: group 13 has 3, 14 has 4, 15 has 5, 16 has 6, 17 has 7, 18 has 8 (He is 2).
Source: entermedschool.org