7.5: Atomic Properties and Periodic Trends

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^-