Answer :
To determine the formal charges on carbon and nitrogen in the cyanide ion (CN⁻), we need to calculate the formal charges using the formula:
Formal Charge (FC) = Valence Electrons - Non-bonding Electrons - (Bonding Electrons / 2)
Here, let’s break it down:
1. Identify Valence Electrons:
- Carbon has 4 valence electrons.
- Nitrogen has 5 valence electrons.
- The cyanide ion (CN⁻) carries an extra electron, so we consider it in our calculations.
2. Determine Electron Configuration:
- For the most stable structure of CN⁻:
- Carbon might be involved in three bonds (as it forms a triple bond with nitrogen) and will have 1 lone electron.
- Nitrogen, bonded to carbon via a triple bond, will have 2 lone electrons (as it originally has 3 pairs and is now sharing 3 through bonding).
3. Calculate Bonding and Non-bonding Electrons:
- Carbon:
- Non-bonding Electrons: 1
- Bonding Electrons: In a triple bond with nitrogen, carbon shares 6 electrons (triple bond), so it contributes half of them in bonding. That is 3 for carbon.
- Total: 1 non-bonding + 3 (half of 6 bonding electrons)
- Nitrogen:
- Non-bonding Electrons: 2
- Bonding Electrons: For nitrogen, similarly, it shares 6 electrons in the triple bond, thus 3 are attributed as bonding for formal charge purposes.
- Total: 2 non-bonding + 3 (half of 6 bonding electrons)
4. Calculate Formal Charges:
- Carbon:
- Valence electrons = 4
- Non-bonding = 1
- Bonding = 3
- FC for Carbon = 4 - 1 - 3 = 0
- Nitrogen:
- Valence electrons = 5
- Non-bonding = 2
- Bonding = 3
- FC for Nitrogen = 5 - 2 - 3 = 0
So, the formal charges for the cyanide ion CN⁻ are:
- Formal charge on carbon: 0
- Formal charge on nitrogen: 0
Therefore, both carbon and nitrogen exhibit a neutral formal charge in the CN⁻ ion under typical counting methods. However, due to a mistake in the external calculation method, it shows incorrect results (1.5 and 0.0) likely due to an error in evaluating the values for electron distribution.
Formal Charge (FC) = Valence Electrons - Non-bonding Electrons - (Bonding Electrons / 2)
Here, let’s break it down:
1. Identify Valence Electrons:
- Carbon has 4 valence electrons.
- Nitrogen has 5 valence electrons.
- The cyanide ion (CN⁻) carries an extra electron, so we consider it in our calculations.
2. Determine Electron Configuration:
- For the most stable structure of CN⁻:
- Carbon might be involved in three bonds (as it forms a triple bond with nitrogen) and will have 1 lone electron.
- Nitrogen, bonded to carbon via a triple bond, will have 2 lone electrons (as it originally has 3 pairs and is now sharing 3 through bonding).
3. Calculate Bonding and Non-bonding Electrons:
- Carbon:
- Non-bonding Electrons: 1
- Bonding Electrons: In a triple bond with nitrogen, carbon shares 6 electrons (triple bond), so it contributes half of them in bonding. That is 3 for carbon.
- Total: 1 non-bonding + 3 (half of 6 bonding electrons)
- Nitrogen:
- Non-bonding Electrons: 2
- Bonding Electrons: For nitrogen, similarly, it shares 6 electrons in the triple bond, thus 3 are attributed as bonding for formal charge purposes.
- Total: 2 non-bonding + 3 (half of 6 bonding electrons)
4. Calculate Formal Charges:
- Carbon:
- Valence electrons = 4
- Non-bonding = 1
- Bonding = 3
- FC for Carbon = 4 - 1 - 3 = 0
- Nitrogen:
- Valence electrons = 5
- Non-bonding = 2
- Bonding = 3
- FC for Nitrogen = 5 - 2 - 3 = 0
So, the formal charges for the cyanide ion CN⁻ are:
- Formal charge on carbon: 0
- Formal charge on nitrogen: 0
Therefore, both carbon and nitrogen exhibit a neutral formal charge in the CN⁻ ion under typical counting methods. However, due to a mistake in the external calculation method, it shows incorrect results (1.5 and 0.0) likely due to an error in evaluating the values for electron distribution.
