Nonmetals generally have varying numbers of valence electrons, but they commonly have 4, 5, 6, 7, or 8 valence electrons. The number of valence electrons for nonmetals is determined by the group number they belong to in the periodic table.
Group 14 nonmetals, such as carbon (C) and silicon (Si), have 4 valence electrons. Group 15 nonmetals, such as nitrogen (N) and phosphorus (P), have 5 valence electrons. Group 16 nonmetals, such as oxygen (O) and sulfur (S), have 6 valence electrons. Group 17 nonmetals, known as the halogens (e.g., fluorine (F) and chlorine (Cl)), have 7 valence electrons. Group 18 nonmetals, the noble gases (e.g., helium (He) and neon (Ne)), have 8 valence electrons, except for helium, which has only 2 valence electrons.
These valence electrons are the electrons in the outermost energy level (shell) of the nonmetal atom and play a crucial role in determining their chemical properties and reactivity.