CN Draw the Lewis dot structure for CN Include all lone pairs of electrons_
The Correct Answer and Explanation is:
Lewis Dot Structure for CN⁻ (Cyanide Ion)
The Lewis dot structure for CN⁻ (cyanide ion) is:
mathematicaCopyEdit:⁻C≡N:
or more fully:
mathematicaCopyEdit.. ..
:C≡N:⁻
Where:
- Carbon (C) and Nitrogen (N) are triple bonded (≡).
- Carbon has one lone pair (two dots).
- Nitrogen has one lone pair.
- The overall structure carries a negative charge (⁻).
Explanation:
The cyanide ion (CN⁻) is a diatomic ion composed of a carbon atom bonded to a nitrogen atom. To understand and draw its Lewis structure, we follow these steps:
1. Determine Total Valence Electrons:
- Carbon has 4 valence electrons.
- Nitrogen has 5 valence electrons.
- The negative charge (⁻) adds 1 extra electron.
- Total = 4 + 5 + 1 = 10 valence electrons.
2. Arrange Atoms:
Carbon and nitrogen are placed side by side: C — N.
3. Create Bonds:
Start by forming single, double, and then triple bonds between C and N to satisfy the octet rule. A triple bond (≡) is necessary to fulfill the octet rule for both atoms efficiently while using the fewest electrons.
4. Assign Lone Pairs:
After forming the C≡N bond (6 electrons used), we place the remaining 4 electrons (10 total – 6 bonding = 4 left) as lone pairs:
- 2 electrons on carbon → 1 lone pair.
- 2 electrons on nitrogen → 1 lone pair.
Each atom now has 8 electrons around it:
- Carbon: 6 (bonding) + 2 (lone pair) = 8.
- Nitrogen: 6 (bonding) + 2 (lone pair) = 8.
5. Assign Formal Charges:
Formal charge = (Valence e⁻) – (Nonbonding e⁻) – (½ × Bonding e⁻)
- Carbon: 4 – 2 – (6/2) = 4 – 2 – 3 = -1
- Nitrogen: 5 – 2 – (6/2) = 5 – 2 – 3 = 0
This gives an overall charge of –1, consistent with the CN⁻ ion.
Thus, the Lewis structure of CN⁻ shows a triple bond and lone pairs on both atoms, with the negative charge residing on the carbon atom.
