Chapter 4
Arrangement of Electrons in Atoms
SECTION 1
1. In what way does the photoelectric effect support the particle theory of light?
In order for an electron to be ejected from a metal surface, the electron must be
struck by a single photon with at least the minimum energy needed to knock the
electron loose.
2. What is the difference between the ground state and the excited state of an atom?
The ground state is the lowest energy state of the atom. When the atom absorbs
energy, it can move to a higher energy state, or excited state.
3. Under what circumstances can an atom emit a photon?
A photon is emitted when an atom moves from an excited state to its ground
state or to a lower-energy excited state.
4. How can the energy levels of the atom be determined by measuring the light emitted from
an atom?
When an atom loses energy, it falls from a higher energy state to a lower energy
state. The frequency of the emitted light, observed in an element’s line-emission
spectrum, may be measured. The energy of each transition is calculated using the
equation E _ hv, where v is the frequency of each of the lines in the element’s line emission
spectrum. From the analysis of these results, the energy levels of an atom
atom of each element may be determined.
5. Why does electromagnetic radiation in the ultraviolet region represent a larger energy
transition than does radiation in the infrared region?
Energy is proportional to frequency, and ultraviolet radiation has a higher frequency
than infrared radiation. To produce ultraviolet radiation, electrons must drop to
lower energy levels than they do to produce infrared radiation.
6. Which of the waves shown below has the higher frequency? (The scale is the same for each
drawing.) Explain your answer.
Wave B has the higher frequency. Wavelength is inversely proportional to
frequency, so as the wavelength decreases, its frequency increases.
7. How many different photons of radiation were emitted from excited helium atoms to
form the spectrum shown below? Explain your answer.
Six different photons were emitted. Each time an excited helium atom falls back
from an excited state to its ground state or to a lower energy state, it emits a
photon of radiation that shows up as this specific line-emission spectrum. There are
six lines in this helium spectrum.
PROBLEMS Write the answer on the line to the left. Show all your work in the space
provided.
8. 9.7 x 1014 Hz
9. 9.4 x 109 m
Handout 13.1
Part A Completion
1. electrons
2. John Dalton
3. J.J. Thomson
4. plum-pudding
5. nucleus
6. circular
7. quantum mechanical
8. probability
Part B True/False
9. AT 11. NT 13. AT
10. ST 12. AT 14. AT
Part C Matching
15. c
17. a
16. b
18. d
Part D Questions and Problems
19. Dalton proposed that matter was made of
indestructible particles called atoms.
Thomson proposed an atomic model in
which negatively charged electrons were
embedded in a positively charged mass.
Rutherford discovered that atoms are mainly
empty space. He proposed that electrons
surround a dense nucleus. Bohr proposed
that electrons are arranged in concentric
circular paths around the nucleus. According
to Bohr, the electrons in a particular orbit
have a fixed energy, which prevents them
from falling into the nucleus. In the modern
atomic theory, the locations of electrons are
not fixed; they are described in terms of
probability.
20. a. 3 orbitals
c. 7 orbitals
b. 5 orbitals
d. 1 orbital
Handout 13.2
Part A Completion
1. electron configurations
2. Aufbau principle
3. equal
4. Pauli exclusion
5. two
6. opposite
7. a single electron
8. superscripts
9. electrons
10. Chromium
Part B True/False
11. ST 13. NT 15. AT
12. NT 14. AT 16. NT
Part C Matching
17. e
19. b
21. c
18 d
20. a
Part D Questions and Problems
22. a. 1s22s22p2
b. 1s22s22p63s23p4
c. 1s22s22p63s23p64s1
d. 1s22s22p63s23p6
23. a. Ar b. B
Handout13.3
Part A Completion
1. waves
2. inversely
3. light
4. atomic emission spectrum
5. light radiation
6. photoelectric
7. frequency
Part B True/False
8. NT 10. AT 12. NT
9. NT 11. NT
Part C Matching
13. c
15. e
17. b
14 a
16. d
Part D Questions and Problems
18. 1.25 x 1015Hz
19. The photoelectric effect will not occur unless
the frequency of the light striking a metal is
high enough to cause an electron to be ejected
from the metal. The frequency of the light
must be above the threshold frequency that
will provide the necessary quanta of energy.
Handout Chapter 4 section 2
1d
2a
3a
4c
5c
6c
7c
9. Principal quantum number , n, energy level of the electron (1, 2, 3, 4, 5, 6, 7)
Angular momentum quantum number, l, sublevel of the electron (s=0, p=1, d=2, f=3 etc.)
Magnetic quantum number, m, orbital orientation (-3,-2, -1, 0, 1, 2, 3)
Spin quantum number, s, spin of the electron in the orbital (-½, ½)
10 Since the position and direction of the electron cannot be known simultaneously we can only
calculate the probability of finding an electron in a given shape around the nucleus.
11
1
s
2
s,p
3
s,p,d
4
s,p,d,f
Handout chapter 4 section 3
1. No 2 electrons in an atom can have the same principal quantum numbers.
Since each orbital can hold 2 electrons and the first 3 quantum numbers only
specify the orbital, the last quantum number must be able to identify 1 of 2
electrons therefore up spin or down spin.
2. This condition can exist if this atom of Helium is in the excited state.
3. P 1S22S22P63S23P3 ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑ ↑ ↑
1S 2S
2P
3S
3P
4. N 1S22S22P3
↑↓ ↑↓
1S 2S
↑ ↑ ↑
2P
5. K 1S22S22P63S23P64S1 ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓
1S 2S
2P
3S
6. Al 1S22S22P63S23P1 ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓
1S 2S
2P
3S
↑↓ ↑↓ ↑↓ ↑
3P
4S
↑ __ __
3P
7. Ar 1S22S22P63S23P6 ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓
1S 2S
2P
3S
3P
8. B 1S22S22P1 ↑↓ ↑↓ ↑ __ __
1S 2S
2P
9 a. Pauli is violated
b. Hund’s rue is violated