Honors Chemistry Worksheet – Configurations
NEATLY provide the best, complete, detailed, yet concise answers to the following questions or
problems.
Orbitals, electrons, and their arrangements
An electron configuration is a method of indicating the arrangement of electrons about a
nucleus. A typical electron configuration consists of numerical coefficients, letters, and
superscripts indicating the following information:
The numerical coefficient indicates the energy level (It also represents the principal quantum
number; n).
The letter indicates energy sublevel or the type of orbital; s, p, d, f, etc.
The superscript indicates the number of electrons in that energy sublevel. e.g. ls2 means that
there are two electrons in the ‘s’ orbital of the first energy level. e.g. 4d4 indicates there are four
electrons occupying the 4th energy level “d” energy sublevel.
Writing electron configurations.
Determine the total number of electrons to be represented.
For neutral atoms the number of electrons equals the number of protons (Z).
For ions, subtract or add electrons to account for the ions charge.
Use the Aufbau principle to fill the orbitals with electrons. The Aufbau principle states that the
electrons will occupy those positions of least energy first.
3. The sum of the superscripts should equal the total number of electrons placed in the atom or
ion.
e.g. Mg0
Z = 12 so place 12 electrons
ls2 2s2 2p6 3s2 superscript sum is 2 + 2 + 6 + 2 = 12
Write Ground State Configurations for Each of the Following:
Assume each atom to be neutral. The ground state configuration would represent arrangement of
least energy.
1.) Na 2.) Pb
3.) Sr
4.) U
5.) N
6.) Ag 7.) Ti
8.) Ce 9.) Cl
10.) Hg
Write a Ground State Electron Configuration for these Ions.
Ions are electrically charged particles. Atoms become ions when they lose (cations) or gain
(anions) electrons.
e.g. P3- Z = 15 so 15 e- + 3 e- is 18 e- total
1.) O2-
2.) Fe2+
3.) B3+
4.) Ni2+
5.) K+
so it is 1s2 2s2 2p6 3s2 3p6.
6.) F-
7.) Se-2 8 .) Co3+
Honors Chemistry Worksheet – Configurations
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The excited state of an atom represents any state other than the ground state. This occurs when
electrons in the atom absorb exciting energy. Excited atoms are unstable energetically. The
electrons eventually fall into a lower E level through the emission of energy.
e.g. An excited configuration for sodium might be
1s2 2s2 2p6 4s1
Write an Excited State Electron Configuration for each Element.
1.) Al
2.) Ar
3.) Ca
4.) O
Provide the best response to each of the following questions.
1. How many “s” orbitals can there be in an energy level?
2. Is it possible for two electrons in the same atom to have exactly the same set of quantum
numbers? Explain.
3. Why do the fourth and fifth periods of elements contain 18 elements, rather than 8 as do the
second and third series?
4. How many “f” orbitals can there be in an energy level? in an “f sublevel?
5. What is the maximum number of electrons that can be present in an atom having three
principal energy levels?
6. How many “p” orbitals can there be in an energy level?
7. What is the shape of an “s” orbital?
8. What is meant by the electron configuration of an atom?
9. Isoelectronic species are different elements (different Z’s) that have the same electron
configurations. Which of these are isoelectronic?
(a) Li+, H-, He
(b) Ca2+, Ne, S210. Which of the following notations shows the electron configuration of a neutral atom in an
excited state? Name the element, and explain how you know it is excited:
(a) 1s2 2s22p1
(b) 1s2 2s22p3 3s1
(c) 1s2 2s2 2p6 3s2 3p1
11. Which is the lowest energy level having “d” orbitals?
12. What is the shape of a “p” orbital?
13. Distinguish between an atom in its ground state and an excited atom.
Honors Chemistry Worksheet – Configurations
Page 3
14. How many electrons can occupy an “s” orbital?
15. For the following elements list the noble gas electron configuration. For four elements or
ions of your choice, write the orbital diagram.
a. boron
e. radon
j. nickel
n. neon
b. cadmium c. phosphorus
f. iodine
g. strontium
k. iron
l. astatine
o. bromine 1- ion
p. xenon
d. rubidium + ion
h. chromium +3 ion
m. silicon 4- ion
q. europium 3+ ion
16. Which is the lowest energy level that can have a “p” orbital?
17. How many energy levels are partially or fully occupied in a neutral atom of calcium?
18. How many “d” electrons can there be in an energy level?
19. Which is the lowest energy level that can have an “s” orbital?
20. What does the term principal quantum number refer to? What is its symbol?
21. How many “f” electrons can there be in an energy level?
22. Which is the lowest energy level having “f” orbitals?
23. For the following electron configurations, choose 3 possible elements (or ions) they may
represent
a. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4
b. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
c. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
d. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1
e. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d8
f. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f10
g. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p4
h. 1s2 2s2 2p6 3s2 3p6 4s2 3d5
i. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2
j. [Kr] 5s2 4d10 5p3
k. [Kr] 5s2 4d10 5p6
l. [Ar] 4s1
Honors Chemistry Worksheet – Configurations
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m. [Xe] 6s2 4f10
n. [Xe] 6s2 4f14 5d7
o. [Ne] 3s2 3p1
24. If each orbital can hold a maximum of two electrons, how many electrons can each of the
following sublevels hold?
a. 2s
b. 5p
c. 4f
d. 3d
e. 4d
25. Which sublevels of the 3rd energy level are filled (a) in the element argon (b) in the element
krypton?
26. Why does it take more energy to remove an electron from Al+ than from Al?
27. For the following elements list the electron configuration. If there is no charge listed,
assume it is neutral.
a. oxygen
b. cesium
c. krypton
d. titanium
e. scandium f. nitrogen
g. chlorine
h. fluorine (1-) ion
i. arsenic
j. francium
k. selenium (2-) ion
l. copper (1+) ion
m. potassium (+1) ion n. antimony (3+) ion o. mercury (2+) ion
Honors Chemistry Worksheet – Configurations –ANSWER KEY
NEATLY provide the best, complete, detailed, yet concise answers to the following questions or
problems.
Orbitals, electrons, and their arrangements
An electron configuration is a method of indicating the arrangement of electrons about a
nucleus. A typical electron configuration consists of numerical coefficients, letters, and
superscripts indicating the following information:
The numerical coefficient indicates the energy level (It also represents the principal quantum
number; n).
The letter indicates energy sublevel or the type of orbital; s, p, d, f, etc.
The superscript indicates the number of electrons in that energy sublevel. e.g. ls2 means that
there are two electrons in the ‘s’ orbital of the first energy level. e.g. 4d4 indicates there are four
electrons occupying the 4th energy level “d” energy sublevel.
Writing electron configurations.
Determine the total number of electrons to be represented.
For neutral atoms the number of electrons equals the number of protons (Z).
For ions, subtract or add electrons to account for the ion’s charge.
Use the Aufbau principle to fill the orbitals with electrons. The Aufbau principle states that the
electrons will occupy those positions of least energy first.
3. The sum of the superscripts should equal the total number of electrons placed in the atom or
ion.
e.g. Mg0
Z = 12 so place 12 electrons
ls2 2s2 2p6 3s2 superscript sum is 2 + 2 + 6 + 2 = 12
Write Ground State Configurations for Each of the Following:
Assume each atom to be neutral. The ground state configuration would represent arrangement of
least energy.
1.) Na 2.) Pb
3.) Sr
4.) U
5.) N
6.) Ag 7.) Ti
8.) Ce 9.) Cl
10.) Hg
Na – 1s2 2s2 2p6 3s1
Pb – 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p2
Sr – 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
U – 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f4
N – 1s2 2s2 2p3
Ag – 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d10 (Note unpredicted difference)
Ti – 1s2 2s2 2p6 3s2 3p6 4s2 3d2
Ce – 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f1 5d1 (Note unpredicted
difference)
Cl – 1s2 2s2 2p6 3s2 3p5
Hg - 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10
Write a Ground State Electron Configuration for these Ions.
Ions are electrically charged particles. Atoms become ions when they lose (cations) or gain
(anions) electrons.
e.g. P3- Z = 15 so 15 e- + 3 e- is 18 e- total
1.) O2-
2.) Fe2+
3.) B3+
4.) Ni2+
5.) K+
so it is 1s2 2s2 2p6 3s2 3p6.
6.) F-
7.) Se-2 8 .) Co3+
O2- - 1s2 2s2 2p6
Fe+2 – 1s2 2s2 2p6 3s2 3p6 3d6 (Note electrons lost are from the valence shell
FIRST!)
B3+ - 1s2
Ni+2 – 1s2 2s2 2p6 3s2 3p6 3d8
K+ - 1s2 2s2 2p6 3s2 3p6
F- - 1s2 2s2 2p6
Se-2 – 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
Co+3 - 1s2 2s2 2p6 3s2 3p6 3d6
Honors Chemistry Worksheet – Configurations
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The excited state of an atom represents any state other than the ground state. This occurs when
electrons in the atom absorb exciting energy. Excited atoms are unstable energetically. The
electrons eventually fall into a lower E level through the emission of energy.
e.g. An excited configuration for sodium might be
1s2 2s2 2p6 4s1
Write an Excited State Electron Configuration for each Element.
1.) Al
2.) Ar
3.) Ca
2
2
6
2
Alex – 1s 2s 2p 3s 4p1
4.) O
Arex – 1s2 2s2 2p6 3s2 3p5 4d1
Caex – 1s2 2s2 2p6 3s2 3p6 4s1 5p1
Oex - 1s2 2s2 2p3 4s1
Provide the best response to each of the following questions.
1. How many “s” orbitals can there be in an energy level?
One s orbital per E level
2. Is it possible for two electrons in the same atom to have exactly the same set of quantum
numbers? Explain.
No. According to the Pauli exclusion principle, no two electrons can have the
same set of four quantum numbers. The repulsive forces of the electrons and
parallel magnetic fields created would not permit them to remain in the same
orbital.
3. Why do the fourth and fifth periods of elements contain 18 elements, rather than 8 as do the
second and third series?
As the energy levels/shells increase in size, there is more room available for
housing electrons. Therefore, increasing energy levels have increasing numbers
of sublevels (or orbitals) which means greater numbers of electrons may be held.
Therefore, period four includes a 3d sublevel increasing the electrons held by ten,
as does period 5 which has a 4d sublevel.
4. How many “f” orbitals can there be in an energy level? in an “f sublevel?
Seven f orbitals in an energy level and seven f orbitals in an energy sublevel.
5. What is the maximum number of electrons that can be present in an atom having three
principal energy levels?
18 electrons – 2 in the 1s, 8 in the 2s & 2p, and 8 in the 3s & 3p. The next place
electrons would appear is the 4s, hence, the 3d electrons would not be included
for a ground state atom.
6. How many “p” orbitals can there be in an energy level?
Three p orbitals per energy level
7. What is the shape of an “s” orbital?
s orbitals are spherical in shape
8. What is meant by the electron configuration of an atom?
The electron configuration of an atom provides the relative positions (and hence
relative energies) of the electrons present in the atom.
9. Isoelectronic species are different elements (different Z’s) that have the same electron
configurations. Which of these are isoelectronic?
(a) Li+, H-, He
(b) Ca2+, Ne, S2+
Li , H , and He are all isoelectronic having a common configuration of 1s2.
Ca+2 and S2- are isoelectronic having a common configuration of 1s2 2s2 2p6
3s2 3p6
10. Which of the following notations shows the electron configuration of a neutral atom in an
excited state? Name the element, and explain how you know it is excited:
(a) 1s2 2s22p1
(b) 1s2 2s22p3 3s1
(c) 1s2 2s2 2p6 3s2 3p1
(b) represents an excited state atom as there is an electron in a position of
higher energy (3s1) while positions of lower energy (2p) are available. The
atom is an atom of oxygen as there are 8 electrons and the atom is neutral
meaning there are 8 protons (Z = 8)
11. Which is the lowest energy level having “d” orbitals?
The lowest energy level with a d sublevel is n = 3. For which l has values of 0, 1,
and 2. An l value of 2 corresponds to the d sublevel.
12. What is the shape of a “p” orbital?
The shape of a p orbital is that of a dumbbell centered about some axis.
13. Distinguish between an atom in its ground state and an excited atom.
An atom in the ground state will have all electrons occupying positions of least
energy whereas, an excited state atom will have an electron(s) in position(s) of
higher energy while there are positions of lower energy available for occupation.
Honors Chemistry Worksheet – Configurations
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14. How many electrons can occupy an “s” orbital?
An s orbital may hold 0, 1, or 2 electrons.
15. For the following elements list the noble gas electron configuration
a. boron
b. cadmium c. phosphorus
d. rubidium + ion
e. radon
f. iodine
g. strontium
h. chromium +3 ion
j. nickel
k. iron
l. astatine
m. silicon 4- ion
n. neon
o. bromine 1- ion
p. xenon
q. europium 3+ ion
B [He] 2s22p1
Cr+3 [Ar] 3d3
Cd [Kr] 5s2 4d10
Ni [Ar] 4s2 3d8
P [Ne] 3s2 3p3
Fe [Ar] 4s2 3d6
Rb+ [Ar] 4s2 3d10 4p6
At [Xe] 6s2 4f14 5d10 6p5
16. Which is the lowest energy level that can have a “p” orbital?
n = 2, because a p sublevel corresponds to an l value of 1 which first appears
when n = 2
17. How many energy levels are partially or fully occupied in a neutral atom of calcium?
There are three energy levels used for the electrons of calcium; n = 1, n = 2, n = 3,
and n = 4
18. How many “d” electrons can there be in an energy level?
A total of ten d electrons may be present in an energy level
19. Which is the lowest energy level that can have an “s” orbital?
All energy levels have an s sublevel, therefore; n = 1
20. What does the term principal quantum number refer to? What is its symbol?
The term principal quantum number, symbol “n”, refers to the energy level or
quantum level and provides relative size and energy of the orbital
21. How many “f” electrons can there be in an energy level?
A total of fourteen electrons may be present in an energy level, n
22. Which is the lowest energy level having “f” orbitals?
The lowest energy level having f orbitals is n = 4. The l value corresponding to an
f sublevel is l = 3, this first appears for n = 4 when l has values of 0, 1, 2, and 3
23. For the following electron configurations, choose 3 possible elements (or ions) they may
represent
a. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4
b. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
c. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
d. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1
e. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d8
f. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f10
g. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p4
h. 1s2 2s2 2p6 3s2 3p6 4s2 3d5
i. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2
j. [Kr] 5s2 4d10 5p3
k. [Kr] 5s2 4d10 5p6
l. [Ar] 4s1
Honors Chemistry Worksheet – Configurations
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m. [Xe] 6s2 4f10
n. [Xe] 6s2 4f14 5d7
o. [Ne] 3s2 3p1
24. If each orbital can hold a maximum of two electrons, how many electrons can each of the
following sublevels hold?
a. 2s
b. 5p
c. 4f
d. 3d
e. 4d
a. two electrons b. six electrons
c. fourteen electrons
d. ten electrons
e. ten electrons
25. Which sublevels of the 3rd energy level are filled (a) in the element argon (b) in the element
krypton?
(a) Argon has electrons filling the 3s and 3p
(b) Krypton has electrons filling the 3s, 3p, and 3d
26. Why does it take more energy to remove an electron from Al+ than from Al?
An Al+ ion has lost an electron decreasing electron – electron repulsion. That
decrease allows the nucleus to pull on the remaining electrons (electron cloud)
bringing it closer to itself and therefore binding it with greater force. Thus, more
energy would be required to remove an additional electron.
27. For the following elements list the electron configuration. If there is no charge listed,
assume it is neutral.
a. oxygen
b. cesium
c. krypton
d. titanium
e. scandium f. nitrogen
g. chlorine
h. fluorine (1-) ion
i. arsenic
j. francium
k. selenium (2-) ion
l. copper (1+) ion
m. potassium (+1) ion n. antimony (3+) ion o. mercury (2+) ion
a. 1s2 2s2 2p4
e. 1s2 2s2 2p3 3s2 3p6 4s2 3d2
j. 1s2 2s2 2p3 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1
k. 1s2 2s2 2p3 3s2 3p6 4s2 3d10 4p6
m. 1s2 2s2 2p3 3s2 3p6
n. 1s2 2s2 2p3 3s2 3p6 4s2 3d10 4p6 5s2 4d10