Question

which one of the following violates the octet rule?
a cbr₄
b nf₃
c pcl₃
d asf₅

Explanation:

Step1: Analyze \(CBr_4\)

Carbon (\(C\)) has 4 valence electrons. Each bromine (\(Br\)) has 7 valence electrons. In \(CBr_4\), \(C\) forms 4 single bonds with \(Br\) atoms. \(C\) gets \(4 + 4=8\) electrons (octet), and each \(Br\) gets \(7 + 1 = 8\) electrons (octet).

Step2: Analyze \(NF_3\)

Nitrogen (\(N\)) has 5 valence electrons. Each fluorine (\(F\)) has 7 valence electrons. In \(NF_3\), \(N\) forms 3 single bonds with \(F\) atoms. \(N\) gets \(5+3 = 8\) electrons (octet), and each \(F\) gets \(7 + 1=8\) electrons (octet).

Step3: Analyze \(PCl_3\)

Phosphorus (\(P\)) has 5 valence electrons. Each chlorine (\(Cl\)) has 7 valence electrons. In \(PCl_3\), \(P\) forms 3 single bonds with \(Cl\) atoms. \(P\) gets \(5+3 = 8\) electrons (octet), and each \(Cl\) gets \(7+1 = 8\) electrons (octet).

Step4: Analyze \(AsF_5\)

Arsenic (\(As\)) has 5 valence electrons. Each fluorine (\(F\)) has 7 valence electrons. In \(AsF_5\), \(As\) forms 5 single bonds with \(F\) atoms. \(As\) gets \(5 + 5=10\) electrons (violates octet rule, as octet rule is 8 - electron rule for main - group elements in most cases), and each \(F\) gets \(7+1 = 8\) electrons (octet).

Answer:

D. \(AsF_5\)