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Which of the following molecules contains at least one atom that has an odd-electron count (i.e. is a free radical)?

Select one or more:
- NH₃
- HCl
- BBr₃
- O₂N-NO₂
- H₂O
- NO
- SF₆

1 Answer

5 votes

Final answer:

Among the given molecules, NO (nitric oxide) and O₂N−NO₂ (nitrogen dioxide) are examples of free radicals, as they contain an odd number of valence electrons and have unpaired electrons that make them reactive. The correct answer is - O₂N-NO₂, - NO.

Step-by-step explanation:

The molecules that contain at least one atom with an odd-electron count, also known as free radicals, can be identified by considering the valence electrons for each element in the molecule. In this case, the molecules to examine are NH₃, HCl, BBr₃, O₂N−NO₂, H₂O, NO, and SF₆.

Odd-electron molecules can be recognized by having a total number of valence electrons that is an odd number, as they cannot fully satisfy the octet rule for all atoms involved. For instance, nitric oxide, NO, is a known free radical with 11 total valence electrons (5 from nitrogen plus 6 from oxygen), indicating that not all atoms can have eight electrons in their valence shell.

Similarly, nitrogen dioxide, NO₂, has an odd number of valence electrons, totaling 17 (5 from nitrogen and 12 from the two oxygens), making it another example of a stable odd-electron molecule.

The other molecules listed, such as NH₃, HCl, BBr₃, H₂O, and SF₆, do not contain an odd number of electrons and do not qualify as free radicals. Among the options given, NO and O₂N−NO₂ (also known as nitrogen dioxide) are the molecules containing at least one odd-electron. Such molecules are likely to be highly reactive due to the presence of the unpaired electron.

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