Question:medium

Which of the following is electron-deficient?

Updated On: Apr 21, 2026
  • (CH3)2
  • (SiH3)2
  • (BH3)2
  • PH3
Show Solution

The Correct Option is C

Solution and Explanation

The concept of electron deficiency is crucial in understanding various compounds in chemistry. Electron-deficient compounds are those that do not have sufficient electrons to form conventional covalent bonds following the octet rule. Let's analyze the options given to determine which compound is electron-deficient:

  1. (CH3)2: Methane (CH4) is a stable molecule with carbon having a complete octet. Even though it's represented as a dimer here, each carbon in methane forms four covalent bonds, achieving electron stability, hence it is not electron-deficient.
  2. (SiH3)2: Silane (SiH4) is similar to methane in that silicon can use its available orbitals effectively to complete its octet and form stable compounds. This compound typically achieves electron satisfaction and is not considered electron-deficient.
  3. (BH3)2: Borane (BH3) is known for being electron-deficient because boron has only 6 valence electrons in this compound. To achieve stability, BH3 forms dimers (B2H6) through bridging hydrogen atoms, which is a characteristic solution for electron deficiency. Thus, (BH3)2 is electron-deficient.
  4. PH3: Phosphine (PH3) has a sufficient number of electrons for phosphorus to achieve a full octet. Hence, it is not electron-deficient.

Based on the analysis, the correct answer is (BH3)2, as it is electron-deficient due to boron not having a complete octet and the formation of dimer (B2H6) compensates for this deficiency.

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