WA 8 Dearing

7. Explain the meaning of the symbol 4 d 6 . (2 points) (Reference: Chang 7.72) 4 = n or energy level, d = suborbital, 6 = number of electrons in d suborbital 8. For each of the following pairs of subshells, indicate which is higher in energy: (a) 2 s or 2 p , (b) 3 d or 4 p , (c) 4 s or 4 p , (d) 3 d or 4 s . (4 points) (a) 2 s = 2+0=2, 2 p = 2+1=3, 2p higher (b) 3 d = 3+2=5, 4 p =4+1= 5 , 3d & 4p have same energy level (c) 4 s = 4+0=4, 4 p =4+1=5, 4p higher (d) 3 d = 3+2=5, 4 s =4+0=4, 3d higher 9. Explain the meaning of diamagnetic and paramagnetic. Give an example of an element that is diamagnetic and one that is paramagnetic. What does it mean when we say that electrons are paired? (3 points) (Reference: Chang 7.73) Paramagnetic substances contain net unpaired spins and are attracted by a magnet. ↑↑ or↓↓ Diamagnetic substances do not contain net unpaired spins and are slightly repelled by a magnet. ↑↓ or ↓↑ 10. Write the ground-state electron configurations for the following elements: (12 points) a. B = 1 s 2 2 s 2 2 p 1 b. V = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4s 2 3 d 3 c. Ni = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4s 2 3 d 8 d. I = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4s 2 3 d 10 4 p 6 5s 2 4d 10 5p 5 (Reference: Chang 7.89) 11. The electron configuration of a neutral atom is 1 s 2 2 s 2 2 p 6 3s 2 . Name the element. (2 points) Na Sodium (Reference: Chang 7.91) 12. A 368 g sample of water absorbs infrared radiation at 1.06 × 10 4 nm from a carbon dioxide laser. Suppose all the absorbed radiation is converted to heat. Calculate the number of photons at this wavelength required to raise the temperature of the water by 5.00ºC. (4 points) (Reference: Chang 7.107) (1.06 × 10 4 nm) (1x10 -9 ) = 1.06 × 10 -5 m ms∆T = (368g)(4.184 J)(5C) = 7.70 x 10 3 J hc/wavelength = (6.63x10 -34 )(3.00x10 8 m/s ) / (1.06 × 10 -5 nm) = 1.88 x 10 -20 J 7.70 x 10 3 J / 1.88 x 10 -20 J = 4.10 x 10 23 photons 2