Question

1. What is the maximum number of unpaired electrons that can occupy each of the

following subshells?

a. 3p,

b. 5d

c. 2s

d. 4f

2. Identify the specific element that corresponds to each of the following electron

configurations and indicate the number of unpaired electrons for each.

a. 1s

2

2s

2

b. 1s

2

2s

2

2p

4

c. [Ar]4s

1

3d

5

d. [Kr]5s

2

4d

10

5p

4

3.

Note: The atomic radius of an element can be predicted based on its periodic

properties. Atomic radii increase going down a group in the

periodic table,

because successively larger valence-shell orbitals are occupied by electrons.

Atomic radii generally decrease moving from left to right across a period because

the effective nuclear charge increases.

Question:

Using only the periodic table, arrange each set of atoms in order from largest to smallest atomic

radius:

a. K, Li, Cs

b. F, O, N

4.

Note:

The size of ions as measured by ionic radii varies in a systematic manner.

The size of the ion can be explained in part by effective nuclear charge,

Zeff

,

which is the net nuclear charge felt by an electron. The effective nuclear charge

takes into account the actual nuclear charge and the shielding of this charge by

2

inner electrons. When an atom loses electrons, the resulting cation is smaller

both because the remaining electrons experience a larger

Zeff

and because

these electrons are usually in orbitals closer to the nucleus than the electrons

that were lost. The more electrons that are lost, the smaller the ion becomes.

Similarly, when an atom gains electrons, the resulting anion is larger owing to both

increased electron-electron repulsions and a reduction in

Zeff

. The more electrons that

are gained, the larger the ion becomes.

Question:

a.

Rank the following items in order of decreasing radius:

Na

,

Na

+

, and

Na

−

.

b.

Provide a brief explanation for each of the following:

i.

O

2-

is larger than O

ii.

S

2-

is larger than O

2-

iii.

K

+

is larger than Ca

2+

5.

Note: i

onization energy (

Ei

) is the amount of energy required to remove an

electron from a neutral gaseous atom or gaseous ion. Electrons are attracted to

the positively charged nucleus; therefore removing an electron requires energy.

The process is endothermic, and so ionization energies have a positive value.

The first ionization energy (

Ei1

) is the energy associated with the removal of an

electron from the neutral gaseous atom. The reaction is represented for the

generalized atom

X

as

X→X+

+

e−

For example: Na

→

Na

+

+ e

-

The amount of energy required to remove an electron is related to the effective

nuclear charge and the stability of the electron configuration of the atom. It

therefore shows periodic variation generally increasing from left to right in a

period and from bottom to top of a group. In general, metals have lower

Ei1

values than nonmetals. Exceptions to this general trend from left to right occur

when a completely filled s subshell or half-filled p subshell is encountered. These

stable configurations have larger than expected

Eil

values.

2

inner electrons. When an atom loses electrons, the resulting cation is smaller

both because the remaining electrons experience a larger

Zeff

and because

these electrons are usually in orbitals closer to the nucleus than the electrons

that were lost. The more electrons that are lost, the smaller the ion becomes.

Similarly, when an atom gains electrons, the resulting anion is larger owing to both

increased electron-electron repulsions and a reduction in

Zeff

. The more electrons that

are gained, the larger the ion becomes.

Question:

a.

Rank the following items in order of decreasing radius:

Na

,

Na

+

, and

Na

−

.

b.

Provide a brief explanation for each of the following:

i.

O

2-

is larger than O

ii.

S

2-

is larger than O

2-

iii.

K

+

is larger than Ca

2+

5.

Note: i

onization energy (

Ei

) is the amount of energy required to remove an

electron from a neutral gaseous atom or gaseous ion. Electrons are attracted to

the positively charged nucleus; therefore removing an electron requires energy.

The process is endothermic, and so ionization energies have a positive value.

The first ionization energy (

Ei1

) is the energy associated with the removal of an

electron from the neutral gaseous atom. The reaction is represented for the

generalized atom

X

as

X→X+

+

e−

For example: Na

→

Na

+

+ e

-

The amount of energy required to remove an electron is related to the effective

nuclear charge and the stability of the electron configuration of the atom. It

therefore shows periodic variation generally increasing from left to right in a

period and from bottom to top of a group. In general, metals have lower

Ei1

values than nonmetals. Exceptions to this general trend from left to right occur

when a completely filled s subshell or half-filled p subshell is encountered. These

stable configurations have larger than expected

Eil

values.

Answer 1