Textbook Question
Using Lewis symbols and Lewis structures, make a sketch of the formation of NCl3 from N and Cl atoms, showing valence-shell electrons. (b) How many bonds Cl has to make in order to achieve an octet?
11. Bonding & Molecular Structure
Formal Charge
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In the best Lewis structure for CN⁻, what is the formal charge on the nitrogen (N) atom?
A
-2
B
0
C
+1
D
-1
Verified step by step guidance1
Step 1: Begin by drawing the Lewis structure for the cyanide ion (CN⁻). The cyanide ion consists of a carbon (C) atom and a nitrogen (N) atom, with an overall negative charge.
Step 2: Count the total number of valence electrons available for CN⁻. Carbon has 4 valence electrons, nitrogen has 5 valence electrons, and the negative charge adds 1 more electron, totaling 10 valence electrons.
Step 3: Arrange the atoms with carbon bonded to nitrogen. Use a triple bond between carbon and nitrogen to satisfy the octet rule for both atoms. This uses 6 electrons, leaving 4 electrons to be placed as lone pairs.
Step 4: Place the remaining 4 electrons as lone pairs on the nitrogen atom, since carbon already has a complete octet with the triple bond.
Step 5: Calculate the formal charge on the nitrogen atom using the formula: \( \text{Formal Charge} = \text{Valence Electrons} - \text{Non-bonding Electrons} - \frac{\text{Bonding Electrons}}{2} \). For nitrogen, this is \( 5 - 4 - \frac{6}{2} = -1 \).
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