7: The Structure of Atoms and Periodic Trends

The Pauli Exclusion Principle

Exercise \(\PageIndex{1}\)

Which of the following statements concerning the Pauli exclusion principle is/are CORRECT?

1. If two electrons occupy the same orbital they must have opposite spins.
2. No two electrons in an atom can have the same four quantum numbers.
3. Electrons with opposing spins are attracted to each other.

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

Answer

d. 1 and 2

 

Quantum Numbers and Electron Configuration

Exercise \(\PageIndex{2}\)

How many electrons can be described by the following quantum numbers: n = 4, l = 2,  = 2, m_s = \(-1\frac{1}{2}\)?

a. 1        b. 2        c. 6        d. 10        e. 18

Answer

a. 1

Exercise \(\PageIndex{3}\)

How many electrons can be described by the following quantum numbers: n = 3, l = 2, m_l = 1?

a. 1        b. 2        c. 6        d. 10        e. 18

Answer

b. 2

Exercise \(\PageIndex{4}\)

How many electrons can be described by the quantum numbers n= 3 and l= 2?

a. 14        b. 6        c. 2        d. 18        e. 10

Answer

e. 10

Exercise \(\PageIndex{5}\)

What is the maximum number of electrons that can occupy the n = 3 shell?

a. 2        b. 8        c. 18        d. 32        e. 50

Answer

a. 2

Exercise \(\PageIndex{6}\)

What is the maximum number of electrons that can occupy one s orbital?

a. 1        b. 2        c. 6        d. 10        e. 14

Answer

b. 2

Exercise \(\PageIndex{7}\)

Which of the following orbital occupancy designations is incorrect?

a. 2s²        b. 3d⁶        c. 1s²        d. 4p³        e. 3d¹²

Answer

e. 3d¹²

Exercise \(\PageIndex{8}\)

The maximum number of electrons that can be accommodated in a p subshell is

a. 10        b. 2        c. 14        d. 1        e. 6

Answer

e. 6

Exercise \(\PageIndex{9}\)

Which of the following electron configurations is not allowed?

1. 1s²2s²2p²
2. 1s²2s²2p⁴
3. 1s²2s³
4. 1s²2s²2p⁶3s²
5. 1s²2s2²p⁵

Answer

c. 1s²2s³

Exercise \(\PageIndex{10}\)

Which of the following sets of quantum numbers is allowed?

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

Answer

c. n = 4, l = 1,  = 0, m_s = \(-1\frac{1}{2}\)

 

The Aufbau Process

Exercise \(\PageIndex{1}\)

The procedure by which electrons are assigned to (or built up into) orbitals is known as the ____ principle.

a. Aufbau        b. Bohr        c. Planck        d. Hund        e. Pauli

Answer

a. Aufbau 

Exercise \(\PageIndex{2}\)

Which of the following statements is true concerning the electron configuration [Xe]6p2?

1. This configuration cannot be the ground-state electron configuration for a Ba atom because it violates the Pauli exclusion principle.
2. This configuration cannot be the ground-state electron configuration for a Ba atom because it violates Hund's rule.
3. This configuration is the ground-state electron configuration for a Ba atom.
4. This configuration cannot be the ground-state electron configuration for a Ba atom because it violates the Heisenberg uncertainty principle.
5. This configuration cannot be the ground-state electron configuration for a Ba atom because it violates the Aufbau principle.

Answer

e. This configuration cannot be the ground-state electron configuration for a Ba atom because it violates the Aufbau principle.

Exercise \(\PageIndex{3}\)

According to the Aufbau principle, which of the following subshells is typically filled next after the 4s subshell?

a. 3d        b. 4s        c. 3p        d. 2p        e. 2s

Answer

a. 3d 

Exercise \(\PageIndex{4}\)

Which of the following statements is/are CORRECT for an oxygen atom?

1. The effective nuclear charge felt by a 2s electron is greater than that felt by a 1s electron.
2. The effective nuclear charges felt by 2s and 2p electrons are identical.
3. The effective nuclear charge felt by a 2p electron is less than that felt by a 2s electron.

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

Answer

c. 3 only

Exercise \(\PageIndex{5}\)

The small, but important, energy differences between 3s, 3p, and 3d electrons is a consequence of

1. the number of electrons they can hold
2. their principal quantum number
3. the Heisenberg uncertainty principle
4. thier effective nuclear charge
5.  Hund's rule

Answer

d. thier effective nuclear charge

Exercise \(\PageIndex{6}\)

Which of the following statements is true?

1. Outer electrons efficiently shield one another from nuclear charge.
2. Core electrons effectively shield outer electrons from nuclear charge.
3. Valence electrons are the most difficult of all electrons to remove.
4. Core electrons have the lowest ionization energies of all electrons.
5. Valence electrons in the outermost shell of all elements have the highest ionization energy.

Answer

b. Core electrons effectively shield outer electrons from nuclear charge.

 

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 = \(+\frac{1}{2}\)

 

Electron Configuration of Ions 

Exercise \(\PageIndex{1}\)

For which of the following atoms is the 2+ ion diamagnetic in the ground state?

a. Ni        b. Fe        c. Zn        d. Mn        e. Cu

Answer

c. Zn

Exercise \(\PageIndex{2}\)

Which of the following elements in its 1+ ionic state has the ground state electron configuration [Kr]4d¹⁰?

a. Ru        b. Au        c. Ag        d. In        e. Cd

Answer

c. Ag

Exercise \(\PageIndex{3}\)

If the ground state electron configuration of an element is [Ar]3d¹⁰4s²4p⁵, what is the typical charge on the monatomic anion of the element?

a. 4+        b. 2+        c. 1-        d. 2-        e. 3-

Answer

c. 1-

Exercise \(\PageIndex{4}\)

What is the ground state electron configuration for Cr³⁺?

1. [Ar]
2. [Ar]3d⁷4s²
3. [Ar]3d¹4s²
4. [Ar]3d²4s¹
5. [Ar]3d³

Answer

e. [Ar]3d³

Exercise \(\PageIndex{5}\)

What is the ground state electron configuration for Sn²⁺?

1. [Kr]4d¹⁰5s²
2. [Kr]4d¹⁰5p²
3. [Kr]5s²
4. [Kr]4d¹⁰5s²5p²
5. [Kr]4d¹⁰5s²5p⁴

Answer

a. [Kr]4d¹⁰5s²

Exercise \(\PageIndex{6}\)

Which of the given ions have the same ground state electron configuration: S^2–, N^3–, Mg²⁺, and Br^–?

1. N^3– and Mg²⁺
2. S^2–, N^3–, and Br^–
3. S^2– and Br^–
4. Mg²⁺ and Br^–
5. S^2–, N^3–, Mg²⁺, and Br^–

Answer

a. N^3– and Mg²⁺

Exercise \(\PageIndex{7}\)

Which of the following has the same (total) number of electrons as Ar?

a. Na⁺        b. Ca²⁺        c. Ga³⁺        d. O^2-        e. none    

Answer

b. Ca²⁺

Exercise \(\PageIndex{8}\)

What is the ground-state electron configuration of the chloride ion?

1. 1s²2s²2p⁶
2. 1s²2s²2p⁶3s²3p²
3. 1s²2s²2p⁶3s²3p⁶
4. 1s²2s²2p⁶3s²
5. 1s²2s²2p⁶3s²3p⁴

Answer

Add texts here. Do not delete this text first.

Exercise \(\PageIndex{9}\)

What 2– ion has the following ground state electron configuration?

1. Oxide ion
2. Nitride ion
3. Fluoride ion
4. Sulfide Ion
5. Magnesium Ion

Answer

d. Sulfide Ion

Exercise \(\PageIndex{10}\)

What 2+ ion has the following ground state electron configuration?

a. Mn²⁺        b. Co²⁺        c. Ni²⁺        d. Cu²⁺        e. Ge²⁺

Answer

b. Co²⁺

Exercise \(\PageIndex{11}\)

Which of the following ions has the given ground state electron configuration?

a. Cd²⁺        b. Sr²⁺        c. Zn²⁺        d.Sn²⁺        None of these

Answer

d. Sn²⁺

Exercise \(\PageIndex{12}\)

The ground-state electron configuration of a Ni²⁺ ion is 1s²2s²2p⁶3s²3p⁶3d⁸ . Therefore, Ni²⁺ is

1. paramagnetic with two unpaired electrons.
2. diamagnetic.
3. paramagnetic with one unpaired electron.
4. paramagnetic with four unpaired electrons.
5. paramagnetic with five unpaired electrons.

Answer

a. paramagnetic with two unpaired electrons.

Exercise \(\PageIndex{13}\)

Which of the following cations has the same number of unpaired electrons as Fe²⁺?

a. Ni²⁺        b. Fe³⁺        c. Cr²⁺        d. Mn²⁺        e. Co²⁺

Answer

c. Cr²⁺

 

Atomic Radius

Exercise \(\PageIndex{1}\)

Which of the following statements is true of atomic radii?

1. They decrease down a group and remain constant across a period.
2. They decrease down a group and increase across a period.
3. They increase down a group and increase across a period.
4. They increase down a group and remain constant across a period.
5. They increase down a group and decrease across a period.

Answer

e. They increase down a group and decrease across a period.

Exercise \(\PageIndex{2}\)

An atom of which of the following elements has the smallest atomic radius?

a. F        b. Rb        c. Ca        d. Ge        e. P

Answer

a. F  

Exercise \(\PageIndex{3}\)

Which of the following atoms of elements has the largest atomic radius?

a. Ga        b. In        c. Al        d. Tl        e. B

Answer

d. Tl

Exercise \(\PageIndex{4}\)

Rank the following atoms in order decreasing atomic radii: Br, Bi, Be, B.

1. B > Br > Be > Bi
2. Be > B > Br > Bi
3. Bi > Be > Br > B
4. Be > Br > Bi > B
5. B > Bi > Be > Br

Answer

a. B > Br > Be > Bi

Exercise \(\PageIndex{5}\)

Place the following atoms in order of increasing atomic radii: Se, Sb, Br, and Te.

1. Br < Se < Te < Sb
2. Se < Br < Sb < Te
3. Se < Br < Te < As
4.  Sb < Te < Se < Br
5. Te < Sb < Se < Br

Answer

a. Br < Se < Te < Sb

 

Ionization Energy (Ionization Potential)

Exercise \(\PageIndex{6}\)

An atom of which of the following elements has the smallest ionization energy?

a. At        b. Bi        c. Pb        d. Cs        e. Po

Answer

d. Cs 

Exercise \(\PageIndex{7}\)

Which of the following statements is/are CORRECT?

1. For any element, the second ionization energy is larger than the first ionization energy.
2. Ionization energy is a positive value for all elements.
3. Ionization energy increases down a group of the periodic table.

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

Answer

d. 1 and 2

Exercise \(\PageIndex{8}\)

The change in energy for which of the following processes corresponds to the first ionization energy of beryllium?

1. Be(g) → Be⁺(g) + e^–
2. Be(s) → Be⁺(s) + e^–
3.  Be(s) → Be⁺(g) + e^–
4. Be(g) → Be²⁺(g) + 2e^–
5. Be(s) + e^– → Be^–(s) 

Answer

a. Be(g) → Be+(g) + e–

Exercise \(\PageIndex{9}\)

Which of the following equations corresponds to the second ionization of magnesium?

1. Mg(g) → Mg⁺(g) + e^–
2. Mg(g) → Mg⁺(g) + e^–
3. Mg(g) → Mg⁺(g) + e^–
4. Mg(g) → Mg²⁺(g) + 2e^–
5. Mg(g) + e^– → Mg^–(g)

Answer

c. Mg(g) → Mg+(g) + e–

Exercise \(\PageIndex{10}\)

For which one of the following elements is the second ionization energy over ten times larger than its first ionization energy?

a. B        b. N        c. Li        d. Ne        e. Cu

Answer

c. Li

Exercise \(\PageIndex{11}\)

Arrange F, Cl, and Br in order of their increasing first ionization energies.

1. F < Cl < Br
2. Cl < F < Br
3. Cl < Br < F
4. Br < F < Cl
5. Br < Cl < F

Answer

e. Br < Cl < F

 

Electron Affinity 

Exercise \(\PageIndex{12}\)

The change in energy for the following reaction is referred to as the ____ for boron.

B(g) + e^– → B^–(g)

1. oxidation number
2. electron affinity
3. electronegativity energy
4. first ionization energy
5. second ionization energy

Answer

b. electron affinity

Exercise \(\PageIndex{13}\)

An atom of which of the following elements has the most negative electron affinity?

a. K        b. Sb        c. Cl        d. Br        e. O

Answer

c. Cl

Exercise \(\PageIndex{14}\)

_____ have no affinity for electrons.

1. Transition metals
2. s-block elements
3. Main group nonmetals
4. Noble gases
5. Semiconductors

Answer

d. Noble gases

Exercise \(\PageIndex{15}\)

According to the general trend in electron affinities, which group (or family) of elements tends to form the most stable anions in the gas phase?

1. Noble gases
2. Halogens
3. Transition metals
4. Alkaline earth metals
5. Alkali metals

Answer

b. Halogens

 

Ionic Radius

Exercise \(\PageIndex{16}\)

Which group of the periodic table of elements forms only 2⁺ ions?

1. group 1A
2. group 2A
3. group 1B
4. group 7A
5. group 8A

Answer

b. group 2A

Exercise \(\PageIndex{17}\)

Rank the following ions in order of decreasing ionic radii: Be²⁺, Ca²⁺, Mg²⁺.

1. Be²⁺, Ca²⁺, Mg²⁺
2. Mg²⁺, Be²⁺, Ca²⁺
3. Ca²⁺, Be²⁺, Mg²⁺
4. Be²⁺, Mg²⁺, Ca²⁺
5. Ca²⁺, Mg²⁺, Be²⁺

Answer

e. Ca²⁺, Mg²⁺, Be²⁺

Exercise \(\PageIndex{18}\)

Place the following ions in order from smallest to largest ionic radii: K⁺, Na⁺, Mg²⁺, and Al³⁺.

1. Al³⁺ < Mg²⁺ < Na⁺ < K⁺
2. Na⁺ < Mg²⁺ < Al³⁺ < K⁺
3. K⁺ < Mg²⁺ < Na⁺ < Al³⁺
4. K⁺ < Al³⁺ < Mg²⁺ < Na⁺
5. Mg²⁺ < Al³⁺ < Na⁺ < K⁺

Answer

a. Al³⁺ < Mg²⁺ < Na⁺ < K⁺

Exercise \(\PageIndex{19}\)

Which of the following species has the largest radius?

a. Cl^–        b. P        c. K^–        d. Br^–        e. Ca²⁺

Answer

d. Br^-

 

 

Trends

Exercise \(\PageIndex{1}\)

Which of the following elements would be expected to have chemical and physical properties most similar to Iodine (I)?

1. Fluorine (F)
2. Aluminum (Al)
3. Magnesium (Mg)
4. Rubidium (Rb)
5. Krypton (Kr)

Answer

a. Fluorine (F)

Exercise \(\PageIndex{2}\)

What is the charge formed by alkaline earth metals when they react with nonmetals?

a. +1        b. −1        c. +2        d. −2        e. +3

Answer

c. +2

Exercise \(\PageIndex{3}\)

A metal oxide forms when potassium reacts with oxygen. What is the most likely formula of this metal oxide?

a. KO        b. K₂O        c. K₂O₃        d. KO₂        e. KO₃

Answer

a. KO

Exercise \(\PageIndex{4}\)

A metal phosphide forms when potassium reacts with elemental phosphorus. What is the most likely formula of this metal phosphide?

a. KP        b. K₃P        c. K₂P₃        d. K₃P₂        e. KP₃

Answer

b. K₃P

Exercise \(\PageIndex{5}\)

A metal halide forms when potassium reacts with elemental chlorine. What is the most likely formula of this metal halide?

a. KCl        b. KCl₂        c. K₂Cl        d. KCl₃        e. K₃Cl₂

Answer

b. KCl₂