Write the Ground-state Electron Configurations of the Following Ions. (a) Li+

3.1: Electron Configurations (Problems)

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PROBLEM \(\PageIndex{1}\)

Using complete subshell notation (no abbreviations), predict the electron configuration of each of the following atoms:

1. C
2. P
3. V
4. Sb
5. Sm

Answer a

1s²2s²2p²

Answer b

1s²2s²2p⁶3s²3p³

Answer c

1s²2s²2p⁶3s²3p⁶3d³4s²

Answer d

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p³

Answer e

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f⁶5s²5p⁶6s².

PROBLEM \(\PageIndex{2}\)

Using complete subshell notation, predict the electron configuration of each of the following atoms:

1. N
2. Si
3. Fe
4. Te
5. Tb

Answer a

1s ²2s ²2p ³

Answer b

1s ²2s ²2p ⁶3s ²3p ²

Answer c

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ⁶

Answer d

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ¹⁰4p ⁶5s ²4d ¹⁰5p ⁴

Answer e

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ¹⁰4p ⁶5s ²4d ¹⁰5p ⁶6s ²4f ⁹

PROBLEM \(\PageIndex{3}\)

Use an orbital diagram to describe the electron configuration of the valence shell of each of the following atoms:

1. N
2. Si
3. Fe
4. Te
5. Mo

Answer a

Answer b

Answer c

Answer d

Answer e

PROBLEM \(\PageIndex{4}\)

Using complete subshell notation (1s ²2s ²2p ⁶, and so forth), predict the electron configurations of the following ions.

1. N^3–
2. Ca²⁺
3. S^–
4. Cs²⁺
5. Cr²⁺
6. Gd³⁺

Answer a

1s ²2s ²2p ⁶

Answer b

1s ²2s ²2p ⁶3s ²3p ⁶

Answer c

1s ²2s ²2p ⁶3s ²3p ⁵

Answer d

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ¹⁰4p ⁶5s ²4d ¹⁰5p ⁵

Answer e

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ²

Answer f

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ¹⁰4p ⁶5s ²4d ¹⁰5p ⁶6s ²4f ⁵

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PROBLEM \(\PageIndex{5}\)

Which atom has the electron configuration: 1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ¹⁰4p ⁶5s ²4d ²?

Answer

Zr

PROBLEM \(\PageIndex{6}\)

Which atom has the electron configuration: 1s ²2s ²2p ⁶3s ²3p ⁶3d ⁷4s ²?

Answer

Co

PROBLEM \(\PageIndex{7}\)

a. Which ion with a +1 charge has the electron configuration 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶?

b. Which ion with a –2 charge has this configuration?

Answer a

Rb⁺

Answer b

Se²⁻

PROBLEM \(\PageIndex{8}\)

Which of the following atoms contains only three valence electrons: Li, B, N, F, Ne?

Answer

B

PROBLEM \(\PageIndex{9}\)

Which of the following has two unpaired electrons?

1. Mg
2. Si
3. S
4. Both Mg and S
5. Both Si and S.

Answer

Although both (b) and (c) are correct, (e) encompasses both and is the best answer.

PROBLEM \(\PageIndex{10}\)

Which atom would be expected to have a half-filled 6p subshell?

Answer

Bi

PROBLEM \(\PageIndex{11}\)

Which atom would be expected to have a half-filled 4s subshell?

Answer

K

PROBLEM \(\PageIndex{12}\)

In one area of Australia, the cattle did not thrive despite the presence of suitable forage. An investigation showed the cause to be the absence of sufficient cobalt in the soil. Cobalt forms cations in two oxidation states, Co²⁺ and Co³⁺. Write the electron structure of the two cations.

Answer

Co^{2 +}: 1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ⁵

Co^{3 +}: 1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ⁴

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PROBLEM \(\PageIndex{13}\)

Thallium was used as a poison in the Agatha Christie mystery story "The Pale Horse." Thallium has two possible cationic forms, +1 and +3. The +1 compounds are the more stable. Write the electron structure of the +1 cation of thallium.

Answer

1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶4d ¹⁰5s ²5p ⁶6s ²4f ¹⁴5d ¹⁰

PROBLEM \(\PageIndex{14}\)

Write the electron configurations for the following atoms or ions:

1. B³⁺
2. O^–
3. Cl³⁺
4. Ca²⁺
5. Ti

Answer a

1s ²

Answer b

1s ²2s ²2p ⁵

Answer c

1s ²2s ²2p ⁶3s ²3p ²

Answer d

1s ²2s ²2p ⁶3s ²3p ⁶

Answer e

1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ²

PROBLEM \(\PageIndex{15}\)

Cobalt–60 and iodine–131 are radioactive isotopes commonly used in nuclear medicine. How many protons, neutrons, and electrons are in atoms of these isotopes? Write the complete electron configuration for each isotope.

Answer

Co has 27 protons, 27 electrons, and 33 neutrons: 1s ²2s ²2p ⁶3s ²3p ⁶4s ²3d ⁷.

I has 53 protons, 53 electrons, and 78 neutrons: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶4d ¹⁰5s ²5p ⁵.

PROBLEM \(\PageIndex{16}\)

Atoms of which group in the periodic table have a valence shell electron configuration of ns ² np ³?

Answer

15 (5A)

PROBLEM \(\PageIndex{17}\)

Atoms of which group in the periodic table have a valence shell electron configuration of ns ²?

Answer

2 (2A)

PROBLEM \(\PageIndex{18}\)

Does a cation gain protons to form a positive charge or does it lose electrons?

Answer

The protons in the nucleus do not change during normal chemical reactions. Only the outer electrons move. Positive charges form when electrons are lost.

PROBLEM \(\PageIndex{19}\)

Iron(III) sulfate [Fe₂(SO₄)₃] is composed of Fe³⁺ and \(\ce{SO4^2-}\) ions. Explain why a sample of iron(III) sulfate is uncharged.

Answer

Two cations with a +3 charge give a total of +6 charge, while three anions of -2 charge give a total of -6 charge. +6-6=0, so when these ions bond, the charges will cancel, leaving the resulting compound uncharged.

PROBLEM \(\PageIndex{20}\)

Which of the following atoms would be expected to form negative ions in binary ionic compounds and which would be expected to form positive ions: P, I, Mg, Cl, In, Cs, O, Pb, Co?

Answer

P, I, Cl, and O would form anions because they are nonmetals. Mg, In, Cs, Pb, and Co would form cations because they are metals.

PROBLEM \(\PageIndex{21}\)

Which of the following atoms would be expected to form negative ions in binary ionic compounds and which would be expected to form positive ions: Br, Ca, Na, N, F, Al, Sn, S, Cd?

Answer

Anions: Br, N, F, S,

Cations: Ca, Na, Al, Sn (because it's a metal), Cd (because it is a metal)

PROBLEM \(\PageIndex{22}\)

Predict the charge on the monatomic ions formed from the following atoms in binary ionic compounds:

1. P
2. Mg
3. Al
4. O
5. Cl
6. Cs

Answer a

P^3–

Answer b

Mg²⁺

Answer c

Al³⁺

Answer d

O^2–

Answer e

Cl^–

Answer f

Cs⁺

PROBLEM \(\PageIndex{23}\)

Predict the charge on the monatomic ions formed from the following atoms in binary ionic compounds:

a. I
b. Sr
c. K
d. N
e. S
f. In

Answer a

I^-

Answer b

Sr²⁺

Answer c

K⁺

Answer d

N^3-

Answer e

S^2-

Answer f

In³⁺

PROBLEM \(\PageIndex{24}\)

Write the noble gas electron configuration for each of the following ions:

a. As^3–
b. I^–
c. Be²⁺
d. Cd²⁺
e. O^2–
f. Ga³⁺
g. Li⁺
h. N^3–
i. Sn²⁺
j. Co²⁺
k. Fe²⁺
l. As³⁺

Answer a

[Ar]4s ²3d ¹⁰4p ⁶

Answer b

[Kr]4d ¹⁰5s ²5p ⁶

Answer c

1s ²

Answer d

[Kr]4d ¹⁰

Answer e

[He]2s ²2p ⁶

Answer f

[Ar]3d ¹⁰

Answer g

1s ²

Answer h

[He]2s ²2p ⁶

Answer i

[Kr]4d ¹⁰5s ²

Answer j

[Ar]3d ⁷

Answer k

[Ar]3d ⁶

Answer l

[Ar]3d ¹⁰4s ²

PROBLEM \(\PageIndex{25}\)

Write out the full electron configuration for each of the following atoms and for the monatomic ion found in binary ionic compounds containing the element:

1. Al
2. Br
3. Sr
4. Li
5. As
6. S

Answer a

Al: 1s ²2s ²2p ⁶3s ²3p ¹

Al³⁺: 1s ²2s ²2p ⁶

Answer b

Br: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁵

Br^-: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶

Answer c

Sr: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶5s ²

Sr²⁺: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶

Answer d

Li: 1s ²2s ¹

Li⁺: 1s ²

Answer e

As: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ³

As^{3 -}: 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶

Answer f

S: 1s ²2s ²2p ⁶3s ²3p ⁴

S^2-: 1s ²2s ²2p ⁶3s ²3p ⁶

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Write the Ground-state Electron Configurations of the Following Ions. (a) Li+

Source: https://chem.libretexts.org/Courses/Oregon_Institute_of_Technology/OIT%3A_CHE_202_-_General_Chemistry_II/Unit_3%3A_Periodic_Patterns/3.1%3A_Electron_Configurations/3.1%3A_Electron_Configurations_(Problems)

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