Questions: Draw the Lewis structure for HCN.

Draw the Lewis structure for HCN.
Transcript text: Draw the Lewis structure for HCN.
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Solution

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Solution Steps

Step 1: Determine the Total Number of Valence Electrons

Hydrogen (H) has 1 valence electron, carbon (C) has 4 valence electrons, and nitrogen (N) has 5 valence electrons. Therefore, the total number of valence electrons in HCN is: \[ 1 + 4 + 5 = 10 \]

Step 2: Arrange the Atoms

The least electronegative atom (excluding hydrogen) is typically placed in the center. In HCN, carbon is the central atom, with hydrogen and nitrogen on either side: \[ \text{H} - \text{C} - \text{N} \]

Step 3: Form Single Bonds

Connect the atoms with single bonds. Each single bond represents 2 electrons: \[ \text{H} - \text{C} - \text{N} \] This uses 4 electrons (2 for each bond).

Step 4: Distribute Remaining Electrons

Distribute the remaining 6 electrons to satisfy the octet rule for each atom (except hydrogen, which only needs 2 electrons):

  • Carbon has 2 electrons from each bond (4 total) and needs 4 more.
  • Nitrogen has 2 electrons from the bond with carbon and needs 6 more.
Step 5: Form Multiple Bonds if Necessary

To satisfy the octet rule for carbon and nitrogen, form a triple bond between carbon and nitrogen: \[ \text{H} - \text{C} \equiv \text{N} \] This uses all 10 electrons (2 for the H-C bond and 6 for the C≡N bond).

Final Answer

The Lewis structure for HCN is: \[ \boxed{\text{H} - \text{C} \equiv \text{N}} \]

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