Problem: The anion (v) is called "BARF" by chemists, as its common abbreviation sounds similar to this word.Which, if any, of these anions has an expanded octet around its central atom?

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We’re being asked to determine which of the given anions contains a central atom that does not follow the octet rule (i.e. an expanded octet)

(i) A central Cl is double bonded on four sides to O. (ii) A central B is single bonded on four sides to F. (iii) A central P is single bonded on six sides to F.(iv) A central Al is bonded to O on four sides. Each O is single bonded to a C that is single bonded to three CF3s. (v) A central B is single bonded on four sides to benzene rings. Each benzene ring is attached to two CF3s.

Recall that the octet rule states that an element is surrounded by eight electrons in the Lewis structure. 


Exceptions to this rule occur when:

• there is an odd number of electrons, like in radicals

• there are less than 8 electrons or incomplete octet

• there are more than 8 electrons or expanded octet. This occurs to nonmetals from Period 3 to 7.




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Problem Details
The anion (v) is called "BARF" by chemists, as its common abbreviation sounds similar to this word.

(i) A central Cl is double bonded on four sides to O. (ii) A central B is single bonded on four sides to F. (iii) A central P is single bonded on six sides to F.(iv) A central Al is bonded to O on four sides. Each O is single bonded to a C that is single bonded to three CF3s. (v) A central B is single bonded on four sides to benzene rings. Each benzene ring is attached to two CF3s.

Which, if any, of these anions has an expanded octet around its central atom?

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