Referring to the most stable Lewis dot structure of CH2F2, what is its molecular geometry?
a. Bent
b. Tetrahedral
c. Trigonal planar
d. Seesaw
The Correct Answer and Explanation is :
The molecular geometry of CH₂F₂ (difluoromethane) is tetrahedral (answer b).
Explanation:
To determine the molecular geometry of CH₂F₂, we first examine its Lewis dot structure. In the Lewis structure, carbon (C) is the central atom bonded to two hydrogen (H) atoms and two fluorine (F) atoms. The structure can be drawn as follows:
- Valence Electrons Count:
- Carbon contributes 4 valence electrons.
- Each hydrogen contributes 1 valence electron (2 total).
- Each fluorine contributes 7 valence electrons (2 total).
- The total count is (4 + 2 + 14 = 20) valence electrons.
- Bonding:
Carbon forms single bonds with two hydrogen atoms and two fluorine atoms. This utilizes 8 valence electrons (4 bonds, 2 electrons each). - Lone Pairs:
After forming the bonds, carbon has no lone pairs, while fluorine atoms each have three lone pairs.
The molecular geometry is primarily determined by the arrangement of the bonding pairs around the central atom. In CH₂F₂, the central carbon atom is surrounded by four bonding pairs (two C-H and two C-F bonds) and no lone pairs. According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, the shape of the molecule is influenced by the repulsion between these electron pairs.
When there are four electron groups (bonding pairs) around a central atom, they will arrange themselves in a tetrahedral geometry to minimize repulsion. This arrangement results in bond angles close to 109.5 degrees, characteristic of tetrahedral molecules.
In conclusion, the stable Lewis structure of CH₂F₂ leads to a tetrahedral molecular geometry, influenced by the arrangement of the four bonding pairs around the central carbon atom. The correct answer is b. Tetrahedral.