Chemistry I-Honors
Electron Arrangement/Quantum Numbers Worksheet
Solution Set
1. What is the frequency of light (EM radiation) if it is known to have a wavelength of 832 cm ?
(Frequency is in units of /sec). [Hint: make sure to use the proper units!] c =   = (3.00 x 10 10 cm/sec) / 832 cm =
- What amount of energy is associated with a photon at this wavelength?
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 E = h  = (6.626 x 10 -34 Joule-sec)( 3.61 x 10 7 sec -1 ) = 2.39 x 10 -26 J
- What amount of energy is associated with a mole of photons at this wavelength?
2.39 x 10 -26 J / 1 photon x (6.02 x 10 23 photons / 1 mol) = 1.44 x 10 -2 J
2. What element is it whose neutral, isolated atom has two valence electrons in the 5s subshell and four electrons in the 5p subshell? 5s 2 5p 4 = Te
3. How many energy levels ( shells ) are either filled or partially filled in the ground state configuration for the neodymiumium atom [ Nd: Atomic #60 ]? [Xe] 6s 2 4f 4 6 shells
4. Based on our knowledge of the energy levels, what would be the predicted atomic number for the next noble gas (VIII-A) after radon (Neglect the hypothetical "g" subshell)?
Z# = 118 (would need another s, p, d, & f subshell = 2 + 6 + 10 + 14)
5. How many valence electrons are there in an arsenic atom? 5
6. Which of the following is an electron configuration of an atom in the excited state?
(May be more than 1) [Excited state is anything out of the normal sequence - higher]
A) 1s 2 2s 1 ; B) 1s 2 2s 2 2p 1 ; C) 1s 2 2s 1 3d 6
; D) 1s 2 2s 1 2p 2 ; E) [Ar] 3d 8 .
7. How many sublevels are either filled or partially filled in an atom of iodine in the ground state?
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 5 = 11 subshells
8. What is the total number of electrons in an atom if the fourth shell has been completely filled?
Ignore any abnormalities in electron configuration, but remember the order as indicated by the
Diagonal Rule and Aufbau Principle. go through 4f
14 already through 6s 2 Z# = 56 + 14 = 70
9. Which quantum number value indicates the most probable distance of the electron from the nucleus of an atom? n
10. The f sublevel contains how many electrons? 14 How many orbitals? 7
11. What is the next subshell to be filled immediately after 6s ? 4f
12. How many filled 3p orbitals are there in a neutral atom of cobalt? all three of them
13. What type of subshell is being filled to make the transition metals? d

14. What type of subshell is being filled to make the rare-earth metals, or inner transition metals? f
15. According to Bohr, the total energy of an electron in an atom is quantized. This means that:
A) an atom's electrons can possess only certain specific amounts of energy;
B) the electrons travel about the nucleus in orbits;
C) the electrons sometimes behave as waves;
D) the position and momentum of an electron cannot be known simultaneously.
16. Which of the following would be expected to have the shortest wavelength?
A) gamma; B) TV; C) visible; D) X rays; E) IR; F) microwave
17. The orbitals within each principal quantum number can be designated by what values?
m = l --- 0 ---- + l
18. The subshells within each principal quantum number can be designated by what values? l = 0, 1, …. n-1
19. What is the maximum number of electrons that can fill any one of the seven "f" orbitals? 2
20. What rule states that no two electrons in the same atom can have the same set of four quantum numbers? Pauli Exclusion Principle
21. What sublevel does the forty-third electron of a neutral polonium atom occupy in the ground state?
same as the highest for Tc = 4d
GIVEN THE FOLLOWING ELECTRON CONFIGURATION:
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 4
Answer the following questions referring to the above configuration:
22. In which sublevel are the electrons of highest energy located? 6p
23. What is the correct chemical symbol for element above? Po
24. What is the number of electron pairs in the 5d orbital? 5
25. This element would most likely be classified as what type of element? chalcogen
26. The correct number of outer shell electrons for this element is how many? 6
27. This element is radioactive - true or false? TRUE
28. How many sublevels are either filled or partially filled? 15
29. T - F This element should be considered to be diamagnetic. False

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30. An orbital is labeled by the magnetic quantum number, m = +2. This could not be found in which subshell(s)? s or p
31. How many electrons can are there in a neutral atom in which the last electron to enter has just filled the 5p orbital? 5p 6 54
32. In a chemical reaction, the removal, or movement, of what type of electrons is associated with the color of the salts of the transition metals? d
33. The idea of electron energy levels in the hydrogen atom was developed by what scientist? Bohr
34. What scientist made a major contribution to science with his work on the photoelectric effect?
Einstein
35. What does the orbital quantum number (m) indicate? which orbital within a subshell
36. The L shell corresponds to which principal quantum number? n = 2
37. Which of the following is(are) a valid set of quantum numbers for one of the electrons in the ground state of a cerium atom? (Not necessarily the last electron.)
Z# = 58 [Xe] 6s 2 4f 2
n l m s
A) 1 0 +1 +1/2 [ +1 for “m” is not a possible value]
B) 5 3 -1 +1/2 [ not yet in the 5f subshell]
C) 2 2 -1 -1/2
D) 1 1 0 +1/2
[ no such thing as a 2d subshell]
[ no such thing as a 1p subshell]
*E) 6 0 0 -1/2
F) 6 2 -2 +1/2 [ not to 6d subshell yet]
G) 4 3 0 +1/2 [ not to 4f 11 ]
*H) 5 0 0 -1/2
38. What is the number of possible orbitals in the d subshell? 5
39. If n represents the principal quantum number of an energy level, what is the number of orbitals in that energy level is equal to? (in a formula form)
2
40. The maximum number of electrons that may occupy a p sublevel is...... 6

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41. Which of the following elements in the fourth series (elements #19 - 36) whose electron configuration appears to be irregular because of the stability of a completely filled sublevel? Cu
42. What element has two filled and one half-filled 5p orbitals in its neutral atom? 5p 5
43. For the Lewis-dot diagram of a neutral silicon atom, how many dots must surround the symbol? 4
[Lewis-dot diagram indicates how many valence electrons are used in bonding.]
44. What rule states that electrons in any subshell tend to stay unpaired as long as possible?
Hund’s Rule
45. What element has five half-filled 4d orbitals in its +2 cationic form? loses its outer 5s 2 electrons to make the cation 4d 5 Tc
46. What is the maximum number of p electrons ( total ) available in a neutral atom of iodine?
47. If a neutral atom loses electrons, what does it become? cation
48. With the exception of helium, a noble gas occurs with the completion of what subshell? p
49. How many electrons are in the outer shell of a neutral strontium atom? 2
50. Which of the following ions is isoelectronic to a neutral atom of krypton? need 36 electrons
A) S -2 ; B) Se -2 ; C) Sr 2+ ; D) Sb -3 ; E) both B and C.
51. What is the amount of energy released if a photon with a wavelength of 4.88 x 10 -14 as an electron drops to ground state?
meters is released
 E = hc /  = (6.626 x 10 -34 Joule-sec)( 3.00 x 10 8 m/sec) / 4.88 x 10 -14 m
= 4.07 x 10 -12 J
52. Given the following set of quantum numbers for the last electron to enter a neutral atom: n = 6 l =
1
m = +1 s = +1/2 What element is it? 6p 3 Bi
53. If a mole of electrons releases 7.73 x 10 -3 joules of energy in the form of photons as they drop to their ground state, what is the wavelength of one of these photons?
7.73 x 10 -3 joules / Av# =

1.28 x 10 -26 joules
 E = hc /  = (6.626 x 10 -34 Joule-sec)( 3.00 x 10 8 m/sec) / 
 = 15.5 m

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54. A cation with a +3 charge has the following electron configuration: [Ar] What element is it? original element had a configuration of [Ar] 4s 2 3d 1
55. What type of electromagnetic radiation has a shorter wavelength than gamma radiation? cosmic radiation
56. Give the complete electron configuration for the nickel +2 ion.
1s 2 2s 2 2p 6 3s 2 3p 6 3d 8 loses its 4s electrons first
57. What is the set of quantum numbers for the last electron that enters the ground state zirconium atom?
4d 2 n = 4 l = 2 m = -1 s = +1/2
58. What is the set of quantum numbers for the 34th electron that enters the ground state uranium atom? same as the last set for Se 4p 4 n = 4 l = 1 m = -1 s = +1/2
59. What is the term for a packet of energy? photon
60. How many filled "p" orbitals are there in a neutral atom of tellurium? 3 + 3 + 3 + 1 = 10
61. Describe the shapes of each of the orbital types.
“s” = spherical “p” = figure-8 “d” = cloverleaf
“f” can only be described in 3-d terms
62. Give a characteristic that distinguishes absorption spectrum from an emission spectrum.
Absorption looks like a rainbow w/ a select few black lines indicating where energy is being absorbed by the electrons. Emission spectra only show a few colored lines when energy is released as electrons drop back to lower (more stable) energy shells.
63. What is the significance of the Heisenberg Uncertainty Principle?
States that both the position and the velocity of an electron in an atom cannot be determined with absolute certainty simultaneously. The more accurately one variable is known, the less accuately the other one is known.

64. What is the significance of de Broglie's wave equation?
Since EM radiation was known to exhibit both particulate properties as well as wave-like behavior, he concluded that matter might be able to do the same. He showed that matter (like electrons) could exhibit a wavelike motion, which allowed the electrons to maintain their energy as they stayed in orbit around the nucleus in an atom.
65. Explain how incandescent lights work. How do fluorescent lights work?
Which is more efficient? Why?
Incandescent bulbs glow because the metal (often tungsten) experiences a high amount of resistance as energy flows through the filament. This energy heats up the filament, causing it to glow.
Fluorescent bulbs are cooler because the gas inside is charged and the energy is released from the gas as the electrons are excited and then dropped back down to the ground state.
Because the incandescent bulbs are constantly being heated and cooled, the filament becomes brittle and breaks. Consequently the bulb needs to be replaced, making this type of bulb less efficient.
66. What importance is a flame test? Who is credited with the development of this test?
Flame tests permits the identification of metals because each metal has a unique arrangement of electrons. The test was first developed by Kirchoff.
67. What color is imparted when sodium is added to a flame?
What color is copper ? Barium ? Lithium ?