To draw the Lewis dot structure for C2H4 (ethylene), we start by determining the total number of valence electrons. Carbon has 4 valence electrons, and hydrogen has 1. With two carbon atoms and four hydrogen atoms, we have:
Total Valence Electrons = (2 x 4) + (4 x 1) = 8 + 4 = 12
In the Lewis structure, each carbon atom will be bonded to two hydrogen atoms and to each other. The structure can be drawn as:
H H
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H - C = C - H
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H H
In this representation, the equal sharing of electrons creates a double bond between the two carbon atoms, while each carbon is also bonded to two hydrogen atoms.
Next, we need to consider the VSEPR (Valence Shell Electron Pair Repulsion) theory to determine the shape of the molecule. Since there are no lone pairs of electrons on the carbon atoms and each carbon forms four bonds (two single bonds and one double bond), the arrangement of electron pairs around each carbon will be trigonal planar.
The name of the shape is trigonal planar because there are three regions of electron density (two C-H bonds and one C=C bond) around each carbon atom. The bond angles in this shape are approximately 120 degrees.
To summarize:
- Shape: Trigonal planar
- Lone pairs of electrons: 0