Week 5-6 Achieve Question 2

[Angela_Li_1J]

For the carbonate lewis structure, the oxygens with a single bond have a formal charge of -1, and since there are two of those oxygens, does the -2 equate to the charge of the carbonate? I was just confused because I calculated that the formal charge was -1 so I put that for the answer and it said it was wrong, and then I put another -1 on the other oxygen, and then the answer was correct.

[Sophia Olender 2J]

Like you said, the carbonate molecule has an overall charge of 2- because of the those two oxygen atoms. Each oxygen atom has a -1 formal charge, so each one needs to have a negative sign in the diagram. The carbon and third oxygen have formal charges of zero so no +/- signs are added.

[Samantha Loc 1B]

Yes, the -1 formal charge on each of the 2 single bonded oxygen atoms leads to the 2- charge of the carbonate.

[Ruben Adamov 1E]

Yes, the two oxygens have a formal charge of -1 each, which means a total of -2. The other atoms have a formal charge of 0. That means the carbonate molecule has a total formal charge of -2.
Hope this helps!

[Shivani Sakthi 1l]

Hello! I thought it might help to do a step-by-step on how to approach this problem.
First, we need the formula of carbonate which is (CO3)2-.
1.) Carbon= 4 electrons, Oxygen= 3 x 6e, and 2 additional electrons because of the 2-, giving us a total of 24 electrons.
2.) We place carbon in the center because it has lower ionization energy.
3.)We will begin by bonding at least one bond from the carbon to each oxygen atom, and then we will proceed to fill up the oxygen octets with lone pairs.
4.) After counting the electrons in the covalent bonds and the octet, 24 electrons are counted. However, Oxygen does not have a full valence shell since it only has 6 electrons. So, we must double bond carbon with one of the oxygens to fill the shell. We must check our formal charges to see if this is the best structure.
5.) Using Fc= V-(c+s/2), we see a 1- charge on each oxygen that are not double-bonded to carbon and a 0 charge on the on the carbon and the oxygen that is double bonded to carbon. So our total formal charge of 2- is apparent. So we must include -1 next to the first two carbons and no charge next to the carbon and the third carbon.

Remember to put brackets around the dot diagram and a negative 2 outside of the brackets, since it is the net formal charge! Hope this helped.