Chemistry 5.0 Chapter 3.3
Name__________________________
I. Locating the Electron:
Period_______Date_______________
A. The maximum number of electrons possible in each principle energy level increases as
shown in the table below.
B. Not all energy levels contain all types of sublevels or orbitals.
C. Energy levels are subdivided into sublevels.
D. Each sublevel contains 1 or more orbitals. An orbital is the name given to a probability
diagram, which describes where an electron can be found.
E. Different orbitals have different shapes.
F. Complete the table below showing the number of orbitals and number of electrons in each
principal energy level.
Energy
Level
Sublevels
available
Number of
orbitals in each
sublevel
Maximum Number of
electrons in each
sublevel
Maximum Number of
electrons in each
energy level
1.
1
s
1
2
2
2.
2
3.
3
4.
4
PROBLEMS:
A. Of the 1s, 2s and 2p sublevels:
1. In which is there no probability of an electron being found near the nucleus? _________
2. In which is there the greatest probability of finding an electron nearest the nucleus? _______
3. In which is there a different probability of finding an electron when going out in different
directions from the nucleus? ________
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B. Of the energy level, sublevel or orbital:
1. Which best pinpoints the probability region in which you can find an electron? ___________
Why?
2. Which pinpoints it the least?_________________ Why?
C. From the table on the previous page, what generalizations can you make regarding:
1. The # of s orbitals in any s sublevel? _______
2. The # of p orbitals in any p sublevel? _______
3. The # of d orbitals in any d sublevel? _______
4. The # of f orbitals in any f sublevel? _______
II. Rules for Locating the Electron:
A. The rules for deciding where the electrons are in an atom are:
1. An electron will always occupy the lowest energy orbital available to it.
2. An orbital, regardless of shape, can hold a maximum of two electrons.
(Pauli Exclusion Principle)
incorrect: ↑↑
correct: ↑↓
3. Electrons will remain unpaired within equal energy orbitals as long as possible.
(Hund’s Rule)
incorrect: ↑↓ ↑ __
correct: ↑ ↑ ↑
Px Py Pz
Px Py Pz
B. An electron configuration is a shorthand notation for indicating the number of electrons
in each sublevel. The notation can be broken down as shown below:
number of electrons in the sublevel
1s2
principle energy level
sublevel (shape of orbital)
C. The order of filling orbitals can be predicted by using the chart shown below: (Aufbau Diagram)
1s2
2s2
2p6
3s2
3p6
3d10
4s2
4p6
4d10
4f14
5s2
5p6
5d10
5f14
6s2
6p6
6d10
6f14
7s2
7p6
7d10
7f14
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PROBLEMS:
A. For each of the following elements, state how many electrons are present in each energy level..
1. beryllium (4 electrons) ___________________________________________________
2. fluorine (9 electrons) ____________________________________________________
3. magnesium (12 electrons) ________________________________________________
4. calcium (20 electrons) ___________________________________________________
B. Write an orbital box diagram and electron configuration for each of the following elements.
1. boron (5 electrons)
2. silicon (14 electrons)
3. argon (18 electron)
4. arsenic (33 electrons)
5. sulfur (16 electrons)
6. magnesium (12 electrons)
C. Look at the following ground state orbital box diagrams, if there is a mistake, correct it.
y
x
1. nitrogen
    
1s
2s
2p
x
2. sodium
z
y
z
    
1s
2s
2p
x

3s
y
z
  
3p
3
y
x
3. phosphorus
2s
2p
y
x
z
3s
z
3p
y
x
z
         
1s
2s
2p
x
5. gallium
y
x
       
1s
4. potassium
z
y
3s
z
3p
y
x
4s
3d
z
              
1s
2s
2p
3s
3p
4s
3d
D. For each of the following changes of orbitals for an electron, state whether the electron would have
to absorb energy or emit energy to complete that change.
1. 3s to 3p
___________________
4.
3p to 2s
___________________
2. 3d to 4s
___________________
5.
5s to 3p
___________________
3. 5s to 4d
___________________
6.
3p to 3d
___________________
E. From the information given, and the periodic table, identify each of the following elements by name.
1. An atom of this element contains 2 electrons in the first energy level, 8 electrons in the
second energy level and 3 electrons in the third energy level. _______________________
2. An atom of this element has the following electron configuration:
1s2 2s2 2p6 3s2 3p6 4s2 3d1
3. An atom of this element has an atomic number of 16.
_______________________
_______________________
F. For each of the following atoms, state whether the electron configuration is written in the ground
state or excited state.
1. oxygen:
1s2 2s2 2p3 3s1
2. potassium: 1s2 2s2 2p6 3s2 3p6 3d1
_________________________
_________________________
3. chlorine:
1s2 2s2 2p6 3s2 3p5
_________________________
4. krypton:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 5s1
_________________________
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III. Valence Electrons / Electron Dot Diagrams:
A. The outtermost energy level is given the name valance energy level. The electrons within
that energy level are known as valence electrons.
B. Determine the number of valence electrons in an element from its electron configuration.
C. There can be a maximum of eight valance electrons and they will be found in the
outtermost s and p orbitals.
PROBLEMS:
A. For each of the following elements, write the electron configurations and then determine
the number of valence electrons.
1. carbon:
2. phosphorus:
3. arsenic:
4. fluorine:
5. silicon:
6. iodine:
7. neon:
8. krypton:
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B. Based on your answers to question A, which of the elements would you expect to
find in the same groups in the periodic table? Why?
C. Write the electron-dot diagram for each of the following elements:
1. strontium
6. calcium
2. oxygen
7. gallium
3. phosphorus
8. aluminum
4. iodine
9. fluorine
5. germanium
10. boron
D. The number of electrons in the valence energy level helps to explain how atoms bond (or
attach to each other). Which elements in question C would you expect to be similar
in their bonding properties based on this statement? Why?
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