Final answer:
To determine the number of electrons in the Lewis structure of formaldehyde (CH2O), one must add up the valence electrons from each atom, which are 4 for carbon, 2 for two hydrogen atoms, and 6 for oxygen, totaling 12 electrons. These are arranged in the Lewis structure with carbon at the center, bonded to hydrogens and oxygen, forming a trigonal planar shape.
Step-by-step explanation:
The question asks us to determine how many electrons must be shown in the Lewis structure of formaldehyde, which has the chemical formula CH2O. To do so, we need to count the total number of valence electrons that each atom contributes. Carbon (C) has four valence electrons, each hydrogen (H) atom has one valence electron, and oxygen (O) has six valence electrons. Adding these together:
- Carbon: 4 electrons
- Hydrogen: 1 electron × 2 = 2 electrons
- Oxygen: 6 electrons
Therefore, the total number of valence electrons is 4 + 2 + 6 = 12 electrons. In the Lewis structure of formaldehyde, carbon is the central atom with two single bonds to hydrogen and one double bond to oxygen, while oxygen also has two lone pairs. The double bond between carbon and oxygen counts as one electron group, and as such, leads to a trigonal planar shape as electron groups repel each other to minimize repulsion. So, the correct answer is C. 12.