Electron Arrangements in
Atoms
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C HAPTER
Chapter 1. Electron Arrangements in Atoms
1
Electron Arrangements in
Atoms
Worksheet
Name _____________________ Class ______________________ Date ________________
Answer each of the questions below to show your achievement of the lesson objectives
Lesson Objective: Understand how to apply the Aufbau principle, the Pauli exclusion principle, and Hund’s
rule to determine ground state electron configurations.
1. An atom’s electron configuration describes
a.
b.
c.
d.
the shape of the electrons
the arrangement of electrons
the shape of electrons
the shape of the orbitals
2. The Aufbau principle states
a.
b.
c.
d.
lower orbitals are filled last
orbitals are filled in random order
lower orbitals are filled before upper orbitals
no lower energy orbitals are filled
3. The Pauli exclusion principle states that
a.
b.
c.
d.
all electrons have four quantum numbers
quantum numbers are excluded for some elements
two electrons in an element may have identical quantum numbers
no two electrons in an element can have the same four quantum numbers
4. Hund’s rule states that
a.
b.
c.
d.
5.
6.
7.
8.
9.
10.
11.
12.
13.
orbitals of equal energy must all have one electron before further filling.
all orbitals must first fill with one electron
energy levels will change as orbitals are filled
orbital filling is a random process
True or False: Each element has a unique electron configuration.
True or False: The 4f orbital fills just after the 4d orbital./li>
True or False: There is one element whose electrons all have the same spin quantum number.
True or False: Carbon has one empty 2p orbital.
True or False: Nitrogen has one 2p orbital that contains two electrons.
The 2p orbital must be filled before the ____ orbital can be filled.
The ______ orbital is filled just before the 3p orbital is allowed to fill.
Each orbital can contain up to _______ electrons.
Boron has ____ empty 2p orbitals.
Lesson Objective: Be able to write correct orbital filling diagrams and electron configurations for all elements.
14. The arrows in orbital filling diagrams indicate
1
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a.
b.
c.
d.
orbital rotation of the electrons
electron spin
magnetic rotation
orientation of orbital
15. Electron configuration superscripts indicate all of the following except
a.
b.
c.
d.
number of electrons
number of protons
atomic number
orbital shapes
16. The electron configuration 1s2 2s2 2p is the electron configuration for
a.
b.
c.
d.
17.
18.
19.
20.
carbon
oxygen
boron
beryllium
True or False: The electron configuration for lithium is 1s2 2s2 .
True or False: Oxygen will have one paired set of 2p electrons.
True or False: The orbital filling diagram for He is ↑ ↑ .
The orbital filling diagram for sodium (atomic number 11) is ____________.
21.
is the orbital filling diagram for ___________.
22. The electron configuration for Al is ___________.
23. 1s2 2s2 2p6 is the electron configuration for _________.
Lesson Objective: Know how to use the noble gas notation shorthand method.
24. The noble gas shorthand method
a.
b.
c.
d.
indicates reactivity
requires writing all the electrons in the diagram
allows abbreviation of the electron configuration
shows relationships among the noble gases
25. True or False: The noble gas configuration for calcium is [Kr]4s2 .
TABLE 1.1:
Element
Ni
Mg
Be
Atomic Number
Electron Configuration
[Ar]3d8 4s2
12
4
Lesson Objective: Be able to determine the number of valence electrons and the number of unpaired electrons
in any atom.
27. Valence electrons are
a. unpaired electrons in the outermost principal energy level
b. all electrons in the outermost orbital
c. electrons in the outermost principal energy level
2
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Chapter 1. Electron Arrangements in Atoms
d. electrons with paired spin in the outermost principal energy level
28.
29.
30.
31.
Note: You may use the electron configuration tables for questions 28-30.
Sc (atomic number 21) has _____ valence electrons.
Chlorine (atomic number 17) would be expected to have _____ unpaired electrons.
Nitrogen (atomic number 7) has _____ valence electrons and ____ unpaired electrons.
Lesson Objective: Understand that some electron configurations are exceptions to the normal Aufbau process.
31. The first element to show an exception to the Aufbau process is
a.
b.
c.
d.
Cr
Pt
Nb
Cs
32. The last of the three rules for determining ground state electron configurations gives information on how to
arrange electrons in a set of orbitals that are all within the same sublevel. Hund’s rule states that orbitals of
equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all of
the unpaired electrons must have the same spin. A slight preference for keeping electrons in separate orbitals
helps minimize the natural repulsive forces that exist between any two electrons.
33. Why do all unpaired electrons need to have the same spin?
34. Develop a method using only the electron configuration tables for determining how many unpaired electrons
a given atom has. Confine your discussion to elements 1-20.
TABLE 1.2:
Element
Ni
Mg
Be
Atomic Number
28
12
4
Electron Configuration
[Ar]3d8 4s2
[Ne]3s2
1s2 2s2
3