Question

1. which of the following atoms or ions does not have 8 valence electrons? a. o² b. f c. s d. mg²+ e. ar

Explanation:

• For \(O^{2 -}\):
• Oxygen (\(O\)) has 6 valence electrons. When it gains 2 electrons to form \(O^{2 -}\), the number of valence electrons becomes \(6 + 2=8\).
• For \(F^{-}\):
• Fluorine (\(F\)) has 7 valence electrons. When it gains 1 electron to form \(F^{-}\), the number of valence electrons becomes \(7+ 1 = 8\).
• For \(S^{-}\):
• Sulfur (\(S\)) has 6 valence electrons. When it gains 1 electron to form \(S^{-}\), the number of valence electrons becomes \(6 + 1=7

eq8\).

• For \(Mg^{2+}\):
• Magnesium (\(Mg\)) has 2 valence electrons. When it loses 2 electrons to form \(Mg^{2+}\), it has a full - shell configuration (similar to neon) with 8 valence electrons.
• For \(Ar\):
• Argon (\(Ar\)) is a noble gas. It has 8 valence electrons in its outermost shell.

Answer:

C. \(S^{-}\)