Use valence bond theory to write the hybridization and bonding scheme for NCCH3. Sketch the model with the right geometry?
1 Answer
Warning! Long Answer. Here's what I get.
Explanation:
Step 1. Draw the Lewis structure
(a) Start with a skeleton structure.
The two
(b) Attach the hydrogen atoms.
The question gives you a clue where they go.
The formula
(c) Add electrons so that every atom gets an octet.
There is only one good way to do it: put a triple bond between the
Step 2. Use VSEPR theory to predict the geometry about each atom.
- The terminal
#"C"# atom: four electron domains (3#"C-H"# bonds and a#"C-C"# bond).
∴ Tetrahedral. - The central
#"C"# atom: two electron domains (a#"C-C"# bond and a#"C≡N"# bond).
∴ Linear. - The
#"N"# atom: two electron domains (a#"C≡N"# bond and a lone pair)
Step 3. Assign hybridizations to each atom
- The terminal
#"C"# atom: tetrahedral. ∴#"sp"^3# hybridized. - The central
#"C"# atom: linear. ∴#"sp"# hybridized. - The
#"N"# atom: two electron domains. ∴#"sp"# hybridized.
Step 4. Sketch the orbitals involved
Here is my drawing (apologies! I'm not a graphics artist).
My drawing may be confusing, so here is a description:
#"H"# atoms: unhybridized#"1s"# orbitals- Terminal
#"C"# atom:#"sp"^3# hybridized; bond angles 109.5° #"C-H"# bonds: σ bonds formed by overlap of#"H 1s"# and#"C sp"^3# orbitals- Central
#"C"# atom:#"sp"# hybridized #"C-C"# bond: σ bond formed by overlap of#"C sp"^3# and#"C sp"# orbitals#"N"# atom:#"sp"# hybridized.#"C≡N"# bond: σ bond formed by overlap of#"C sp"# and#"N sp"# orbitals, plus two bonds formed by side-on overlap of unhybridized#"2p"# orbitals#"C-C-N"# bond angle = 180°
Here's a model of the molecule for comparison:
