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question 28 which one of these molecules does not violate the octet rul…

Question

question 28
which one of these molecules does not violate the octet rule?
nh₃
bf₃
no₂
beh₂
bro₂

Explanation:

Brief Explanations
  • For \(NH_3\):
  • Nitrogen (\(N\)) has 5 valence electrons. Hydrogen (\(H\)) has 1 valence electron.
  • In \(NH_3\), \(N\) forms 3 single bonds with \(H\) atoms. Using the formula for the number of valence - electron pairs around the central atom \(N\): \(\text{Number of valence - electron pairs}=\frac{5 + 3\times1}{2}=4\).
  • The Lewis structure of \(NH_3\) has \(N\) surrounded by 8 electrons (3 bonding pairs and 1 lone pair), so it follows the octet rule.
  • For \(BF_3\):
  • Boron (\(B\)) has 3 valence electrons. Fluorine (\(F\)) has 7 valence electrons.
  • In \(BF_3\), \(B\) forms 3 single bonds with \(F\) atoms. The number of valence - electron pairs around \(B\) is \(\frac{3+3\times7}{2}=12\) (total valence electrons), and the number of electrons around \(B\) is \(6\) (3 bonding pairs), so it violates the octet rule (less than 8 electrons around \(B\)).
  • For \(NO_2\):
  • Nitrogen (\(N\)) has 5 valence electrons. Oxygen (\(O\)) has 6 valence electrons.
  • The total number of valence electrons is \(5 + 2\times6=17\). Since the number of valence electrons is odd, it is impossible for all atoms to follow the octet rule (because the octet rule requires an even number of electrons for full - shell configurations in most cases).
  • For \(BeH_2\):
  • Beryllium (\(Be\)) has 2 valence electrons. Hydrogen (\(H\)) has 1 valence electron.
  • In \(BeH_2\), \(Be\) forms 2 single bonds with \(H\) atoms. The number of electrons around \(Be\) is \(4\) (2 bonding pairs), so it violates the octet rule (less than 8 electrons around \(Be\)).
  • For \(BrO_2\):
  • Bromine (\(Br\)) has 7 valence electrons. Oxygen (\(O\)) has 6 valence electrons.
  • The total number of valence electrons is \(7+2\times6 = 19\). Since the number of valence electrons is odd, it is impossible for all atoms to follow the octet rule (because the octet rule requires an even number of electrons for full - shell configurations in most cases).

Answer:

\(NH_3\)