Question

SbF5 is known but BiF5 is not known. Explain by giving orbital electronic configuration.

Answer 1

Answer on Question #53528 – Chemistry – Inorganic Chemistry

Question:

SbF5 is known but BiF5 is not known. Explain by giving orbital electronic configuration.

Answer:

The electronic configurations of the metals are:

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p³ for Sb

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p³ for Bi.

Since Bi has 6s², which has somewhat lower energy than 4f¹⁴5d¹⁰ it needs much energy to use these electrons for bond formation. Therefore, there is only BiF₃ which is stable. Contrary to Bi, as Sb is in the fifth period it doesn't contain f,d-orbitals with higher energy than s-valence sublevel. So all five electrons are available to form SbF₅. This is called the inert pair effect, when completed sublevels (4f¹⁴5d¹⁰ for Bi), especially for elements from the down periods, interact with valence orbital (5s for Bi) decreasing its energy. This makes it more inert towards interaction with valence orbital of another element (this case F).

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