Which of the following compounds does not follow the octet rule?

Options

A. `SF_2`
B. `CIF_3`
C. `NCl_3`
D. `C Cl_4`

Answer

B

Explanation

The electronic basis of the octet rule is that the one s and three p orbitals in the valence shell of an atom can accommodate a maximum of eight electrons. The valence shell of Cl has `n=3`, so it also has vacant `3d` orbitals available that can be involved in bonding. It is for this reason that Cl (and many other representative elements of period 3 and beyond) can exhibit an expanded valence shell. By contrast, elements in the second row of the periodic table can never exceed eight electrons in their valence shells, because each atom has only one s and three p orbitals in that shell. Thus, we understand why `PF_5` can exist but `NF_5` cannot.