Determine the number of valence electrons in ethanol (C2H5OH) and then draw the corresponding Lewis structure.
The correct answer and explanation is:
Correct Answer:
Ethanol (C₂H₅OH) has 20 valence electrons.
Here is the Lewis structure for ethanol:
H H
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H – C – C – O – H
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H H
Explanation:
To determine the number of valence electrons in ethanol (C₂H₅OH), start by identifying the number of atoms and the valence electrons each type contributes:
- Carbon (C) has 4 valence electrons. There are 2 carbon atoms: 4 × 2 = 8 electrons.
- Hydrogen (H) has 1 valence electron. There are 6 hydrogen atoms: 1 × 6 = 6 electrons.
- Oxygen (O) has 6 valence electrons. There is 1 oxygen atom: 6 × 1 = 6 electrons.
Now add them together:
8 (from carbon) + 6 (from hydrogen) + 6 (from oxygen) = 20 valence electrons total.
Ethanol is a simple organic molecule made up of a two-carbon chain where one carbon (C) is bonded to three hydrogen atoms (forming CH₃), the next carbon (C) is bonded to two hydrogen atoms and an –OH group (forming CH₂OH). The –OH (hydroxyl) group consists of an oxygen atom single-bonded to hydrogen.
In the Lewis structure, each atom must satisfy the octet rule, except for hydrogen, which only needs 2 electrons (a single bond). Here’s how the bonding works:
- The first carbon is bonded to three hydrogens and one carbon.
- The second carbon is bonded to the first carbon, two hydrogens, and one oxygen.
- The oxygen is bonded to the second carbon and one hydrogen, and it has two lone pairs of electrons.
Each bond (single line) represents two electrons. After arranging the atoms and bonds, you distribute any remaining electrons as lone pairs to satisfy the octet rule for carbon and oxygen. Hydrogen atoms are complete with just one bond. This gives a stable structure for ethanol with 20 valence electrons properly accounted for.