Chemistry 103
Homework Problems Answer Key for Chapter 11

1. What does the wavelength of electromagnetic radiation represent? Sketch a representation of a wave indicating the wavelength on your diagram.

Length of one cycle

2. What is a "packet" of electromagnetic energy called?


3. What does it mean to say that an atom is in an "excited state"?

Possesses excess energy

4. How does the Bohr theory account for the observed phenomenon of the emission of discrete wavelengths of light by excited atoms?

Energy levels are fixed and thus the emitted light is also fixed.

5. As an electron moves from one principal energy level to a higher-number level, the distance of the electron from the nucleus (increases/decreases).


6. Although a hydrogen atom has only one electron, the hydrogen atom possesses a complete set of available orbitals. What purpose do these additional orbitals serve?

Empty orbitals serve as excited state orbitals.

7.The energy of a principal energy level (increases/decreases) as n increases.


8. According to the Pauli exclusion principle, a given orbital can contain only ______ electrons.

2 electrons

9. Why is the 1s orbital the first orbital to be filled in any atom?

It is the lowest in energy.

10. Write the full electron configuration (1s22s2, etc.) For each of the following elements.

a. silicon, Z = 14
b. argon, Z = 18
c. magnesium, Z = 12
d. helium, Z = 2

a. Si 1s22s22p63s23p2
b. Ar 1s22s22p63s23p6
c. Mg 1s22s22p63s2
d. He 1s2

11. Write the complete orbital diagram for each of the following elements, using boxes to represent orbitals and arrows to represent electrons.

a. sodium, Z = 11
b. calcium, Z = 20
c. chlorine, Z = 17
d. argon, Z = 18


12. Using the symbols of the previous noble gas to indicate the core electrons,. Write the valence shell electron configuration for each of the following elements.

a. rubidium, Z = 37
b. chlorine, Z = 17
c. phosphorous, Z = 15
d. barium, Z = 56

a. Rb [Kr] 5s1
b. Cl [Ne] 3s23p5
c. P [Ne] 3s23p3
d. Ba [Xe] 6s2

13. How many 3d electrons are found in each of the following elements?

a. nickel, Z = 28
b. iron, Z = 26
c. manganese, Z = 25
d. vanadium, Z = 23

a. Ni 8 d electrons
b. Fe 6 d electrons
c. Mn 5 d electrons
d. V 3 d electrons

14. In each of the following sets of elements, indicate which element shows the most active chemical behavior.

a. Li, K, Cs
b. Mg, Sr, Ra
c. S, Se, Te

a. Cs
b. Ra
c. S

15. Arrange the following sets of elements in order of increasing atomic size.

a. Sn, Xe, Rb, Sr
b. Rn, He, Xe, Kr
c. Pb, Ba, Cs, At

a. Xe<Sn<Sr<Rb
b. He<Kr<Xe<Rn
c. At<Pb<Ba<Cs

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