Draw the correct three-dimensional Lewis structure of FCN (Central atom carbon). Must show all lone pairs with dots and bonded atoms with lines. Then answer the following questions: A. Electron pair geometry: B. Molecular geometry: C. Bond angle: D. Show polarity of bonds by using delta notations (or partial charges).
The Correct Answer and Explanation is:
Here’s the Lewis Structure of FCN (fluorine–carbon–nitrogen) with carbon as the central atom:
rCopyEdit :F:
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.. :F–C≡N:
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Explanation of Structure:
- Carbon (C) is the central atom.
- Fluorine (F) is bonded to carbon via a single bond.
- Nitrogen (N) is bonded to carbon via a triple bond.
- Fluorine has three lone pairs.
- Nitrogen has one lone pair.
A. Electron Pair Geometry:
Linear
B. Molecular Geometry:
Linear
C. Bond Angle:
180°
D. Polarity of Bonds (with δ Notation):
- F–C bond: δ⁻F – δ⁺C
- C≡N bond: δ⁺C ≡ δ⁻N
Explanation:
The molecule FCN, also known as fluoroisocyanide, consists of fluorine (F), carbon (C), and nitrogen (N). In this linear triatomic molecule, carbon is the central atom, forming two bonds: a single bond with fluorine and a triple bond with nitrogen.
Step 1: Drawing the Lewis Structure
Carbon, having four valence electrons, forms a single bond with fluorine and a triple bond with nitrogen, using up all its valence electrons. Fluorine, with seven valence electrons, shares one with carbon and retains three lone pairs. Nitrogen, with five valence electrons, forms three bonds with carbon and retains one lone pair. This satisfies the octet rule for all atoms involved.
Step 2: Geometry
There are two regions of electron density (one single bond and one triple bond) around the central carbon. According to VSEPR theory, two regions of electron density arrange themselves in a linear geometry to minimize repulsion. Hence, both the electron pair geometry and molecular geometry are linear, with a bond angle of 180°.
Step 3: Polarity
The C–F bond is polar due to fluorine’s high electronegativity (δ⁻ on F, δ⁺ on C). The C≡N bond is also polar, with nitrogen being more electronegative (δ⁻ on N, δ⁺ on C). Since both bonds pull electron density in opposite directions, the molecule could appear symmetrical, but the differing bond types and electronegativities make FCN a polar molecule overall.
Thus, FCN is a linear, polar molecule with distinct bond polarity due to electronegativity differences and bond types.
