NAME_________________________________

1) (4 points) Phosphorus has oxoacids with formulas H₃PO₄, H₃PO₃, and H₃PO₂.

a) Draw a Lewis structure for H₃PO₂ (the atom layout is suggested if we write the formula as P(H)(OH)₂).

Central P, single bonded to H and two OH groups. 2 lone pairs on each O, 1 lone pair on P.

b) Calculate the oxidation state for every atom in the Lewis structure by assigning electrons.

P = 1+

O = 2-

H = 1+

2) (4 points) The radial probability distribution function for a 3p orbital, ignoring the constants, is

3) (2 points) A known compound, potassium peroxydisulfate, has the formula K₂S₂O₈. Is it possible to assign reasonable oxidation states for the atoms in this compound? Please support your answer.

Yes. K = 1+, S = 6+ (7+ is unreasonable because it would require loss of a core electron), six O's are 2-, two O's are 1- (peroxide, as suggested by name). 

4) (5 points) A chemist writes a paper in which he claims that he has synthesized the following covalent compounds. The paper is sent to me for review. I write back that 5 of the formulas seem unreasonable on the basis of normal numbers of covalent bonds, assuming that oxygen forms 2 bonds in all cases and that hydrogen and the halogens form 1. Circle the unlikely formulas. UNREASONABLE ONES IN BOLD. JUDGMENT AS TO UNREASONABILITY BASED ON OXIDATION STATE OF CENTRAL ATOM OR ON NORMAL NUMBER OF COVALENT BONDS FORMED BY CENTRAL ATOM.

PO₂F

N₂O₅

SO₂(OH)F

H₃BO₃

P₄O₆

5) (5 points) For each atom indicate the maximum possible number of covalent bonds:

B: period 2, four valence orbitals, four covalent bonds maximum.

C: period 2, four valence orbitals, four covalent bonds maximum.

P: period 3, nine valence orbitals, nine covalent bonds maximum.

Fe: period 3, nine valence orbitals, nine covalent bonds maximum.

Br: period 4, nine valence orbitals, nine covalent bonds maximum.