Draw the Lewis structure for CF+ and indicate both the electron pair geometry and the molecular geometry.
The Correct Answer and Explanation is:
To draw the Lewis structure for CF⁺ (carbon monofluoride cation) and determine both its electron pair geometry and molecular geometry, follow these steps:
1. Count the total valence electrons:
- Carbon (C) has 4 valence electrons.
- Fluorine (F) has 7 valence electrons.
- The positive charge (+1) means we subtract 1 electron.
Total valence electrons: 4 + 7 – 1 = 10 electrons
2. Determine the central atom and connect atoms:
Carbon is less electronegative than fluorine, so C is the central atom, and we place F on the outside.
Draw a single bond between C and F, which uses 2 electrons.
Remaining electrons: 10 – 2 = 8 electrons
3. Complete the octets:
Place 6 electrons as lone pairs around fluorine to complete its octet. That uses 6 electrons.
Remaining electrons: 8 – 6 = 2 electrons
Place the remaining 2 electrons as a lone pair on carbon.
4. Check formal charges:
- Fluorine: 6 non-bonding electrons + 1 bond = 7 (valence) → formal charge = 0
- Carbon: 2 non-bonding + 1 bond = 3 → formal charge = 4 – 3 = +1
This gives the correct +1 charge on the molecule.
5. Lewis structure for CF⁺:
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:F:
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C⁺
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Fluorine has three lone pairs. Carbon has one lone pair.
6. Determine the geometries:
- Electron pair geometry considers all electron regions (bonds and lone pairs). Carbon has 2 regions: one bond to F and one lone pair. This gives a linear electron geometry.
- Molecular geometry considers only atoms. With one atom attached and one lone pair, the molecular geometry is linear as well.
Summary:
- Lewis Structure: Carbon bonded to fluorine with one lone pair on carbon and three on fluorine.
- Electron Pair Geometry: Linear
- Molecular Geometry: Linear
This structure satisfies the octet rule for fluorine and reflects the positive charge on carbon.
