How many valence electrons does a nitrogen atom have? How many are bonding? How many are nonbonding (or lone pairs)? Draw the Lewis Electron-Dot structure for acetonitrile C2H3N, which contains a carbon-nitrogen triple bond
The Correct Answer and Explanation is:
A nitrogen atom has 5 valence electrons. In acetonitrile (C₂H₃N), nitrogen forms a triple bond with a carbon atom, so 3 of those electrons are bonding. The remaining 2 electrons form a nonbonding pair, commonly known as a lone pair.
Here is the Lewis structure for acetonitrile:
H H H
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H–C–C≡N:
Explanation:
To draw the Lewis Electron-Dot structure for acetonitrile, we start by identifying the atoms and their bonding preferences. The molecular formula C₂H₃N tells us there are two carbon atoms, three hydrogen atoms, and one nitrogen atom. Carbon has 4 valence electrons, hydrogen has 1, and nitrogen has 5. The total number of valence electrons is:
- Carbon: 2 × 4 = 8
- Hydrogen: 3 × 1 = 3
- Nitrogen: 5
- Total: 8 + 3 + 5 = 16 valence electrons
The structure begins with a carbon (C) bonded to three hydrogen (H) atoms, forming a methyl group. This carbon is then single bonded to another carbon atom, which is in turn triple bonded to a nitrogen atom. Each hydrogen forms a single bond with the carbon, using one electron pair each.
The triple bond between the second carbon and nitrogen consists of three shared electron pairs. With three bonding pairs used by nitrogen, the remaining pair is nonbonding, completing its octet. This lone pair sits on nitrogen and is not involved in bonding.
This configuration satisfies the octet rule for all atoms. The methyl carbon is surrounded by eight electrons from its three H–C bonds and its C–C bond. The second carbon has one single bond to the methyl carbon and three bonding pairs with nitrogen, also totaling eight electrons.
Understanding how nitrogen distributes its valence electrons illustrates how molecules achieve stability through bonding and lone pairs.
