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Prentice Hall Chemistry © 2005

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1 Prentice Hall Chemistry © 2005
Section Assessment Answers Chapter 5

2 5.1 section assessment Why did Rutherford’s atomic model need to be replaced? It could not explain why metals or compounds of metals give off characteristic colors when heated nor the chemical properties of the elements.

3 5.1 section assessment 2. What was the basic new proposal in the Bohr model of the atom? An electron is found only in specific circular paths or orbits around the nucleus.

4 5.1 section assessment 3. What does the quantum mechanical model determine about electrons in atoms? It determines the allowed energy levels an electron can have and the likelihood of finding an electron in various locations around the nucleus.

5 5.1 section assessment 4. How do two sublevels of the same principal energy level differ from each other? The sublevels have different shapes.

6 5.1 section assessment 5. How can electrons in an atom move from one energy level to another? By losing or gaining just the right amount of energy – a quantum.

7 5.1 section assessment 6. The energies of electrons are said to be quantized. Explain what this means. In an atom, the electrons can have certain fixed energy levels. To move from one energy level to another requires the emission or absorption of an exact amount of energy, or quantum. Thus the energy of the electron is said to be quantized.

8 5.1 section assessment 7. How many orbitals are in the following sublevels? a.3p sublevel b.2s sublevel c. 4p sublevel d. 3d sublevel e. 4f sublevel a. 3 b.1 c.3 d.5 e.7

9 5.2 section assessment 10. What are the three rules for writing the electron configuration of elements? Aufbau principle Pauli exclusion principle Hund’s rule

10 5.2 section assessment 11. Explain why the actual electron configurations for some elements differ from those assigned using the aufbau principle. Half-filled sublevels and filled sublevels are more stable than other configurations.

11 5.2 section assessment 12. Use figure 5.7 to arrange the following sublevels in order of decreasing energy: 2p, 4s, 3s, 3d, and 3p. 3d 4s 3p 3s 2p

12 5.2 section assessment 13. Why does one electron in a potassium atom go into the fourth energy level instead of squeezing into the third energy level along with the eight already there? The 3s and 3p orbitals are already filled, so the last electron must go to the next higher energy orbital, which is 4s.

13 5.3 section assessment 16. How are wavelength and frequency of light related? Frequency and wavelength of light are inversely proportional to each other.

14 5.3 section assessment 17. Describe the cause of atomic emission spectrum of an element. Electrons in atoms absorb energy as they move to higher energy levels, then lose the energy by emitting it as light as they drop back.

15 5.3 section assessment 18. How is the change in electron energy related to the frequency of light emitted in atomic transitions? The light emitted in an electronic transition from a higher to a lower energy level has a frequency that is directly proportional to the energy change of an electron.

16 5.3 section assessment 19. How does quantum mechanics differ from classical mechanics? Quantum mechanics describes the motions of atoms and subatomic particles; classical mechanics describes the motions of larger bodies.

17 5.3 section assessment 20. The lines at the ultraviolet end of the hydrogen spectrum are known as the Lyman series. Which electron transitions within an atom are responsible for these lines? electron transitions from higher levels to n = 1

18 5.3 section assessment 21. Arrange the following in order of decreasing wavelength. a. infrared radiation from a heat lamp b. dental X-rays c. signal from a shortwave radio station. c a b

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