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The number of non-metals varies depending on classification criteria. Some sources count 17-18 non-metals (excluding metalloids), while others count 22-23 (including certain elements). The answer of 22 is consistent with some Indian educational board classifications. Elements classified as non-metals include hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, selenium, and the halogens (F, Cl, Br, I). The noble gases are sometimes counted separately. The exact count depends on whether metalloids like boron, silicon, and germanium are included.