Lewis Structures and Valence Electrons

The video tutorial explains the process of drawing the Lewis structure for Carbonyl Sulfide (COS). It begins by counting the valence electrons and placing Carbon, the least electronegative atom, at the center. Initial bonds are formed between Carbon, Oxygen, and Sulfur. The tutorial then addresses the octet rule by adjusting bonds, forming double bonds to ensure all atoms achieve an octet. The video concludes by explaining why triple bonds are not formed and how the formal charges are minimized to zero, resulting in the most stable Lewis structure for COS.

What is the total number of valence electrons in the COS molecule?

• 12

• 14

• 16

• 18

Which atom is placed at the center of the COS molecule?

• Oxygen

• Sulfur

• Carbon

• Hydrogen

How many valence electrons does Sulfur have in the initial structure?

• 2

• 8

• 4

• 6

What is the main issue with the initial electron distribution in the COS molecule?

• Sulfur has more than 8 electrons

• Oxygen has less than 8 electrons

• Carbon does not have an octet

• There are too many electrons

What adjustment is made to help Carbon achieve an octet?

• Add more electrons to Carbon

• Form a triple bond with Sulfur

• Share electrons with Oxygen

• Remove electrons from Sulfur

Why are triple bonds not formed between Oxygen and Carbon in COS?

• It would use more than 16 electrons

• It would result in incorrect formal charges

• Oxygen and Sulfur cannot form triple bonds

• Carbon cannot form triple bonds

What should the formal charges be for the best Lewis structure?

• All negative

• All positive

• Equal to the number of valence electrons

• As close to zero as possible

What is the formal charge on each atom in the final COS structure?

• +1

• -1

• 0

• +2