One Point Quiz

1. One Point Quiz • One quiz per table, list everyone’s name • Agree on an answer • You have two minutes

2. Formal Charge Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

3. H • • H O H C • • H Formal Charge Assume bonding electrons belong 1/2 to each bonding atom. The formal charge is the net charge on each atom.

4. e–shared 2 H • • H O H C • • H Formal Charge unshared electrons formal charge - = e–donated - formal charge of oxygen 6 valence electrons 4/2 shared electrons 4 unshared electrons = - -

5. 4 - 8/2 - 0 = 0 H • • • • • • • • • • • • • • • • • • • • • • • • H C H O • • • • • • • • • • • • • • • • • • • • • • • • 1 - 2/2 - 0 = 0 H 6 - 4/2 - 4 = 0 C: 4 - 8/2 - 0 = 0 H: 1 - 2/2 - 0 = 0 O: 6 - 4/2 - 4 = 0 Formal Charges of AtomsMethanol Formal charge = valence electrons - electrons shared/2 - electrons not shared Atoms with low formal charges generally indicate the correct bonding pattern of chemically stable molecules.

6. H H • • • • • • • • • H C H H O H C O • • • • • • • • • C: 4 - 6/2 - 2 = -1 C: 4 - 4/2 - 4 = -2 H H H: 1 - 2/2 - 0 = 0 H: 1 - 2/2 - 0 = 0 O: 6 - 6/2 - 2 = +1 O: 6 - 8/2 - 0 = +2 Incorrect Diagrams for Methanol What are the formal charges for each atom in the following structures? Validity Check The sum of the formal charges always equals the charge on the molecule or ion. Validity Check The sum of the formal charges always equals the charge on the molecule or ion.

7. H H H • • • • • • • • • • • • • • • • H H C C H H H O H C O O • • • • • • • • • • • • • • • • C: 4 - 6/2 - 2 = -1 C: 4 - 4/2 - 4 = -2 H H H H: 1 - 2/2 - 0 = 0 H: 1 - 2/2 - 0 = 0 O: 6 - 6/2 - 2 = +1 O: 6 - 8/2 - 0 = +2 Incorrect Diagrams for Methanol If either of these structures was stable, which one would more likely be stable?

8. • • • • • • • • • • • • • • • • • C C N N • • • • • • • • • • • • • • • • • C: 4 - 6/2 - 2 = -1 total charge = -1 Cyanide Ion Lewis Dot diagram Skeleton diagram C 4 valence e– N 5 valence e– charge 1 e– total 10 valence e– Convert to a Lewis Dot diagram N: 5 - 6/2 - 2 = 0 5 e– pairs What are the formal charges for each atom in this ion?

9. • • • • • • • • • • C C N N • • • • • • • • • • C: 4 - 6/2 - 2 = -1 N: 5 - 6/2 - 2 = 0 total charge = -1 Cyanide Ion Which “end” of cyanide ion is negative? Cyanide ion reacts with iron(III) ion to make the hexacyanoferrate(III) ion. Does the iron(III) ion bond to carbon or nitrogen?

10. • • N • • • • 3- • • C • • N • N • • • • • • • • • • • • • C C • • • • Fe • • • • C C • • • • • • • • • • • • • • N N • • • • C • • • • • • • • N • • Hexacyanoferrate(III) ion Carbon is the negative end of the cyanide ion.

11. + H N 5 valence e– + H • • • • H 4 valence e– H N H • • H N H • • charge -1 e– • • H H: 1 - 2/2 - 0 = 0 H total 8 valence e– N: 5 - 8/2 - 0 = +1 total charge = +1 Ammonium Ion Lewis Dot diagram Skeleton diagram Nitrogen usually forms 3 bonds 4 e– pairs Which atoms have a non-zero formal charge? In an ion, some atom must have a non-zero formal charge. Why?

12. Formal Charges • What are the formal charges on the atoms in • hydroxide ion • hydronium ion (oxonium ion)

13. O – O O Cl Chlorate Ion Skeleton diagram usually the unique atom is in the center two possibilities Cl-O-O-O – chain structures are uncommon correct structure

14. • • • • O O • • • • • • • • • • • • O O O O Cl Cl • • • • • • • • • • Cl: 7 - 6/2 - 2 = +2 O: 6 - 2/2 - 6 = -1 O: 6 - 2/2 - 6 = -1 O: 6 - 2/2 - 6 = -1 total charge = -1 Chlorate Ion Lewis Dot diagram Skeleton diagram Cl 7 valence e– O 18 valence e– charge 1 e– total 26 valence e– Only 6 electrons shown (3 pairs) 13 e– pairs Complete the Lewis Dot diagram Why is chlorate ion a good oxidizing agent?

15. Cl 7 valence e– • • • • O O • • O 24 valence e– • • • • • • • • • • • O O Cl • charge 1 e– • • • • • • • • • • Cl: 7 - 8/2 - 0 = +3 • • O O • • total 32 valence e– • • O: 6 - 2/2 - 6 = -1 O: 6 - 2/2 - 6 = -1 O: 6 - 2/2 - 6 = -1 O: 6 - 2/2 - 6 = -1 total charge = -1 Perchlorate Ion Lewis Dot diagram Skeleton diagram O O Cl Only 8 electrons shown (4 pairs) 16 e– pairs Why are organic perchlorate salts potentially explosive?

16. Pair ActivityFormal Charges • Develop a procedure to determine the formal charges on a molecule or ion. • Initially, one person should be responsible for writing all the information. • The other person should be responsible for saying what should be written.

17. Pair ActivityFormal Charges • On a card or a piece of paper • write each sequential step necessary to determine the formal charges. • number each step. • amend and update the list. • Determine the formal charges on • acetic acid, CH3COOH • acetate ion, CH3COO–

18. • • • • • • • • H H H • • O O O • • • • • • H H C H C H C C C C • • • • O H H H • • O O • • • • • • • • C: 4 - 8/2 - 0 = 0 C: 4 - 8/2 - 0 = 0 H: 1 - 2/2 - 0 = 0 H: 1 - 2/2 - 0 = 0 O: 6 - 4/2 - 4 = 0 O: 6 - 2/2 - 6 = -1 O: 6 - 4/2 - 4 = 0 O: 6 - 4/2 - 4 = 0 total charge = 0 total charge = -1 Acetic Acid and Acetate Ion

19. Formal Charges • What are the formal charges on the atoms in • ozone • sulfite ion • sulfur trioxide

20. C 4 valence e– • • 2- 2- • • O O • • O 18 valence e– • • • • • • • • • • O C O • charge 2 e– O C • • O • • • • • total 24 valence e– Carbonate Ion Lewis Dot diagram “Connection” diagram Which oxygen atom has the double bond? Convert to a Lewis Dot diagram 12 e– pairs