Question

expansion of octet is not observed in
1.SF4
2.PCl5
3.NH3
4.XeF2​

Answer 1

The expansion of octet is not observed in 3.NH3

The expansion of octet is observed in PCl5,SF4 and XeF2...where the central atom ends up with more than an octet

Answer 2

3. The expansion of octet is not observed in $NH_3$

Explanation:

• S has six valence electrons. In sulfur tetrafluoride $SF_4$ when sulfur, S bonds with four Fluorine atoms, the number of electrons around it becomes 10. Thus, it is an expanded octet.
• P has five valence electrons. In phosphorus pentachloride $PCl_5$ when phosphorus, P bonds with five chlorine atoms, the number of electrons around it becomes 10. Thus, it is an expanded octet.
• N has five valence electrons. In ammonia $NH_3$ when nitrogen, N bonds with three hydrogen atoms, the number of electrons around it becomes 8. Thus, it is not an expanded octet.
• Xenon has eight valence electrons. In xenon difluoride $XeF_2$  when xenon, Xe bonds with two Fluorine atoms, the number of electrons around it becomes 10. Thus, it is an expanded octet.