Final answer:
The species likely to violate the octet rule is XeO3 (xenon trioxide), as the xenon atom can expand its valence shell beyond eight electrons, forming additional bonds. The correct option in the final answer is (d) XeO3.
Step-by-step explanation:
The student's question concerns the identification of a chemical species where the central atom is likely to violate the octet rule. The octet rule states that atoms tend to bond in such a way that they have eight electrons in their valence shell, giving them the same electronic configuration as a noble gas. However, some atoms can have more or less than eight electrons around them. The given choices are NH₃ (ammonia), CHCl₂, SiCl₄ (silicon tetrachloride), XeO₃ (xenon trioxide), and BF₄⁻ (tetrafluoroborate ion).
Out of the options provided, the compound XeO₃ is likely to violate the octet rule because xenon, being a noble gas, can expand its valence shell beyond eight electrons, allowing it to form additional bonds. Xenon can form stable compounds such as XeF₂ and XeF₄, both of which are known to have more than eight electrons around the xenon atom. Similarly, in xenon trioxide, the central xenon atom also exceeds the eight-electron configuration.
The other molecules listed generally obey the octet rule, with silicon and boron being known for forming compounds with exactly eight and six electrons in their valence shells, respectively. Ammonia (NH₃) also typically obeys the octet rule for nitrogen.
Hence, the correct option in the final answer indicating the species that is likely to violate the octet rule is (d) XeO₃.