7.3: Electron Configuration of Atoms

Electron Configuration 

Exercise \(\PageIndex{1}\)

Which of the following elements is found in the d-block of the periodic table?

1. Ir
2. Tb
3. Li
4. Cl
5. None of these

Answer

a Ir

Exercise \(\PageIndex{2}\)

An element that has the same ground state valence-shell electron configuration as thallium is

a. gallium        b. carbon        c. krypton        d. cesium        e. magnesium

Answer

a. gallium 

Exercise \(\PageIndex{3}\)

How many valence electrons does an arsenic atom have?

a. 5        b. 8        c. 7        d. 2        e. 33

Answer

a. 5

Exercise \(\PageIndex{4}\)

How many unpaired electrons are found in the ground state electron configuration of Barium (Ba)?

a. 0        b. 1        c. 2        d. 3        e. 5

Answer

a. 0

Exercise \(\PageIndex{5}\)

Which of the following orbital diagrams represents a paramagnetic atom?

         1s               2s                         2p

1. 
2. 
3. 

a. 1 only        b. 2 only        c. 3 only        d. 1 and 2        e. 2 and 3

Answer

e. 2 and 3

Exercise \(\PageIndex{6}\)

Which of the following atoms is diamagnetic in its ground state?

1. Mercury (Hg)
2. Tin (Sn)
3. Rhenium (Re)
4. Berkelium (Bk)
5. Phosphorus (P)

Answer

a. Mercury (Hg)

Exercise \(\PageIndex{7}\)

Which of the following orbital diagrams represents a diamagnetic atom?

      1s      2s          2p

1. 
2. 
3. 
4. 
5. 

Answer

a. 

Exercise \(\PageIndex{8}\)

Which atom has the ground state electronic configuration 1s²2s²2p⁶3s²3p⁶4s²3d³?

a. Ga        b. V        c. As        d. Nb        e. none

Answer

b. V

Exercise \(\PageIndex{9}\)

Which of the following elements has the ground state electron configuration [Ar]3d¹⁰4s¹?

a. Cu        b. Zn        c. Ge        d. Ag        e. Cd

Answer

a. Cu

Exercise \(\PageIndex{10}\)

What is the ground-state electron configuration of sulfur (S)?

a. [Ne]3s³3sp³        b. [Ar]3s²3p⁴        c. [Ar]3p⁶        d. [Ne]3s²3p⁴        e. [Ar]3p⁶

Answer

d. [Ne]3s²3p⁴

Exercise \(\PageIndex{11}\)

Which of the following electron configurations corresponds to the ground state of an atom of a transition element?

1. 1s²2s²2p¹
2. 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p³
3. 1s²2s²2p⁶3s²3p⁶3d¹4s²
4. 1s²2s²2p⁶3s²3p⁶4s¹
5. 1s²2s²2p⁶3s²3p⁴

Answer

c. 1s²2s²2p⁶3s²3p⁶3d¹4s²

Exercise \(\PageIndex{12}\)

The complete electron configuration of tin is _____.

1. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p²
2. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p²
3. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4d¹⁰4p²
4. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5d¹⁰5p²
5. None of these

Answer

a. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p²

Exercise \(\PageIndex{13}\)

Hund's rule states that the most stable arrangement of electrons (for a ground state electron configuration)

1. has a filled valence shell of electrons.
2. has three electrons per orbital, each with identical spins.

3. has  values greater than or equal to +1.

4. has the maximum number of unpaired electrons, all with the same spin.

5. has two electrons per orbital, each with opposing spins.

Answer

d. has the maximum number of unpaired electrons, all with the same spin.

Exercise \(\PageIndex{14}\)

All of the following ground-state electron configurations are correct except

1. V: [Ar]4s²4d³
2. K: [Ar]4s¹
3. Sb: [Kr]4d¹⁰5s²5p³
4. Cr: [Ar]3d⁵4s¹
5. Te: [Kr]4d¹⁰5s²5p⁴

Answer

a. V: [Ar]4s²4d³

Exercise \(\PageIndex{15}\)

What noble gas core precedes the valence shell ground state electron configuration for potassium (K)?

a. [Ar]        b. [Rn]        c. [Kr]        d. [Ne]        e. [Xe]

Answer

a. [Ar]   

Exercise \(\PageIndex{16}\)

Which ground-state electron configuration is incorrect?

1. Br: [Ar]3d¹⁰4s²4p⁵
2. K: [Ar]4s¹
3. Ni: [Ar]3d⁵
4. Mg: 1s²2s²2p⁶3s²
5. Co: [Ar]3d⁷4s²

Answer

c. Ni: [Ar]3d⁵

Exercise \(\PageIndex{17}\)

Which element has the following ground state electron configuration?

a. Be        b. O        c. Li        d. Si        e. N

Answer

e. N

Exercise \(\PageIndex{18}\)

Which element has the following ground state electron configuration?

3d                                4s

[Ar] 

a. Sc        b. Ni        c. Co        d. Fe        e. V

Answer

a. Sc

Exercise \(\PageIndex{19}\)

Which element has the following ground state electron configuration?

a. In        b. Y        c. Nb        d. Tl        e. Ga

Answer

a. In

Exercise \(\PageIndex{20}\)

Which is the correct valence shell orbital box notation for the ground state electron configuration of Fe?

     3d                                     4s

1. 
2. 
3. 
4. 
5. 

Answer

a. 

Exercise \(\PageIndex{21}\)

What is a possible set of quantum numbers for an unpaired electron in the orbital box diagram below?

1. n = 1, l = 1,  = –1, m_s = \(+\frac{1}{2}\)
2. n = 4, l = 2,  = –1, m_s = \(-1\frac{1}{2}\)
3. n = 5, l = 2,  = –2, m_s = \(+\frac{1}{2}\)
4. n = 5, l = 0,  = 0, m_s = \(-1\frac{1}{2}\)
5. n = 5, l = 1,  = –1, m_s = \(+\frac{1}{2}\)

Answer

e. n = 5, l = 1,  = –1, m_s = \(+\frac{1}{2}\)