Lone Pairs

[Fatima Valenzuela 3k]

In the homework there is a question where we have to draw the structure of CH20 and its lone pairs. How do we know how many lone pairs there are and how would I draw it?

[hadydamaj27]

Start with the highest electronegative element in the middle. Determine the total amount of valence electrons based on the elements on the periodic table. After drawing the structure and the bonds, the leftover valence electrons that are not in the bond are the lone pairs, meaning they are not shared with the other atom.

[Kai Johnson 3B]

To add on to that, make sure each molecule matches its own octet rule. Remember that d-orbital elements can foster more than 8 electrons and can expand to up to 12 as far as we know.

[Brandon Li]

A really easy way to figure out how many electrons are lone pairs (unpaired in bonds) is to first add up the total number of valence electrons in a molecule to get the total electrons in the lewis structure. Then, figure out the bonds of the molecule in its lewis structure, and finally distributing the remaining electrons as lone pairs.

For example:

CO2, has 16 total valence electrons (C has 4 and O has 6 times two)

After drawing the lewis structure, we can see that the two double bonds between C and the two O atoms takes up 8 electrons. Thus, the remaining 8 must be lone pairs. Carbon already has its octet rule filled, so that means the remaining 8 electrons must also be lone pairs of the two O atoms.

Hope this helped