Concept: The general outermost electronic configuration \( ns^2, np^5 \) indicates there are 7 valence electrons. Elements with 7 valence electrons belong to Group 17 (Halogens).
Formula: $$ \text{Valence electrons} = 2 + 5 = 7 $$
Solution: - Let's check the valence configurations for the options:
- Carbon (C, Group 14): \( 2s^2, 2p^2 \) (4 valence electrons)
- Silicon (Si, Group 14): \( 3s^2, 3p^2 \) (4 valence electrons)
- Sulfur (S, Group 16): \( 3s^2, 3p^4 \) (6 valence electrons)
- Chlorine (Cl, Group 17): \( 3s^2, 3p^5 \) (7 valence electrons)
- Chlorine perfectly matches the \( ns^2, np^5 \) pattern.
Why other options are incorrect: They belong to different periodic groups and therefore have different numbers of electrons in their outermost \( p \)-subshell.
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