When drawing Lewis dot structures, it's essential to follow specific rules to create the most stable representation of a molecule. Elements bond to achieve a stable electron configuration similar to that of the nearest noble gas. For example, let's consider the Lewis dot structure for formaldehyde, which has the chemical formula CH₂O.

The first step is to determine the total number of valence electrons in the molecule. Valence electrons correspond to the group number of each element in the periodic table. Carbon, located in group 4, contributes 4 valence electrons. Each hydrogen, from group 1, contributes 1 valence electron, totaling 2 for the two hydrogens. Oxygen, found in group 6, contributes 6 valence electrons. Adding these together gives a total of 12 valence electrons for formaldehyde.

Next, place the least electronegative element in the center of the structure and connect all other elements with single bonds. In this case, carbon is the central atom since hydrogen cannot occupy the center due to its limited capacity for electrons. Thus, we arrange the molecule with carbon in the center, flanked by two hydrogens and one oxygen above it, forming single bonds between them.

Following the octet rule, we need to ensure that surrounding elements have 8 electrons. Hydrogen, however, only requires 2 electrons to achieve stability. Initially, the structure has 2 electrons from the single bonds, and we need to add electrons to oxygen to fulfill its octet requirement. By distributing the remaining electrons, we find that oxygen can accommodate 6 more electrons, bringing its total to 8.

After accounting for the 12 electrons used, we notice that carbon only has 6 electrons around it. To satisfy the octet rule for carbon, we can form a double bond between carbon and oxygen by using one of the pairs of electrons from the oxygen. This adjustment allows carbon to achieve a total of 8 electrons, while oxygen also maintains its octet.

Finally, we can assess the formal charge to ensure the structure is drawn correctly. The formal charge should ideally be -1, 0, or +1, with the negative charge on the more electronegative element for stability. In this case, both carbon and oxygen satisfy the octet rule, and the structure is stable without any formal charges. Thus, the Lewis dot structure for formaldehyde is represented with hydrogen atoms single bonded to carbon, which is double bonded to oxygen, with oxygen holding four non-bonding electrons.