To draw the Lewis structure for formaldehyde ( ext{CH}_4 ext{O}), we start by counting the total number of valence electrons. Carbon (C) has 4, hydrogen (H) has 1 each (total of 4 for 4 hydrogens), and oxygen (O) has 6. This gives us a total of 4 + 4 + 6 = 14 valence electrons.
Next, we construct the skeleton of the molecule. Carbon is the central atom because it can form four bonds. We place oxygen and the four hydrogen atoms around the carbon atom:
In the Lewis structure, the carbon atom is bonded to four hydrogen atoms, forming single bonds, and double bonded to an oxygen atom. Each bond consists of two electrons, resulting in:
- 4 single bonds between C and H = 8 electrons
- 1 double bond between C and O = 4 electrons
This accounts for all 14 valence electrons we have. Now, let’s determine the molecular geometry. The molecule has a tetrahedral geometry due to the four regions of electron density (the four C-H bonds).
Regarding polarity, the difference in electronegativity between carbon and oxygen creates a dipole moment because oxygen is more electronegative than carbon. Since there is an asymmetrical distribution of charge due to the presence of the oxygen atom, CH4O is polar.
In summary:
- Molecular Geometry: Tetrahedral
- Polarity: Polar