chapter 8

Question 1

what are electrons attracted to? repelled by?

Answer 1

attracted to nucleus and repelled by each other

Question 2

what is shielding?

Answer 2

outer electrons (valence) are shielded from the nucleus by core electrons (feel a smaller net charge)

Question 3

do electrons in the outermost orbitals shield each other?

Answer 3

Electrons in the outermost orbitals do not effectively

shield each other from the nuclear charge

Question 4

what is effective nuclear charge? what do Z and S represent?

Answer 4

The effective nuclear charge is net positive charge
that is attracting a particular electron Z is the nuclear charge
• S is the shielding
constant

Question 5

how can Zeffective be found?

Answer 5

Zeffective = Z − S

Question 6

what are trends in radii controlled by?

Answer 6

Trends in the radii of neutral atoms, cations, and anions

is controlled by the effective nuclear charge (Zeff)

Question 7

what happens as we move left to right across a period?

Answer 7

the effective
nuclear charge increases as more protons are added to
the nucleus (Z increases)

Question 8

what can increase Z? what happens to S?

Answer 8

Adding more protons increases Z, while the shielding
constant, S, remains the same for the valence
electrons, therefore Zeff must increase

Question 9

what happens to Zeffective as we move down a group? why?

Answer 9

As you move down a group, the effective nuclear
charge slightly decreases (minimal) : more core
electrons and shielding the same number of valence
electrons

Question 10

what happens to the atomic radius as you move right across the periodic table? down a group?

Answer 10

Atomic radius decreases as you move right across the
periodic table
• Atomic radius increases as you move down a group

Question 11

what happens to the atomic radius as we move across a period (left to right)?

Answer 11

Atomic Radius
Decreases across
period (left to right)

Question 12

what happens as atomic radius decreases?

Answer 12

adding electrons to same
valence shell
- effective nuclear charge
increases
- valence shell held closer

Question 13

what happens to the atomic radius as we go down a group?

Answer 13

Atomic Radius

Increases down group

Question 14

what happens as atomic radius increases?

Answer 14

valence shell farther from
nucleus
- effective nuclear charge
fairly close

Question 15

do transition metals follow trend? what do they do?

Answer 15

The atomic radius of
transition metals do not
follow the trend
- Tend to stay constant across
the d-block

Question 16

what happens to Zeffective for transition metals? when electrons are added?
number of electrons in outermost level ?

Answer 16

The overall Zeff does not change
much between transition
metals.
- As one additional e- is added to
the d-orbital, another proton is
added to the nucleus
- The number of electrons in the
outermost principal energy level
stays the same (ns)

Question 17

what are the d electrons considered for transition metals?

Answer 17

core electrons. will shield each other more so than main group valence/outer shell, so Zeff is more constant.

Question 18

are cations smaller or larger than corresponding atoms? what trend do they follow?

Answer 18

• Cations are
smaller than their
corresponding
atoms • Same trends for
cations as atoms
as you move
across a row or
down a group • Fewer electron
repulsions

Question 19

are anions smaller or larger? electron repulsion?

Answer 19

Anions are larger
than their
corresponding
atoms
• More electrons
increase repulsions
so the radii is larger

Question 20

describe isoelectronic species (3 points)

Answer 20

The same number of electrons
• Can be a mix of cations/anions/noble gas
• Need to consider the number of electrons vs protons
for each species in order to determine which is
larger/smaller

Question 21

what is ionization energy?

exothermic or endothermic?

Answer 21

Energy required to remove an electron
from an atom or ion in the gaseous state
Endothermic process, energy is always
positive

Question 22

which electrons are easiest to remove? what is the ionization energy trend? exceptions?

Answer 22

• Valence electrons are the easiest to
remove
• Generally increase as we move across a
period (rows) and decreases down a group
• Except between 2A & 3A, and 5A & 6A

Question 23

is more or less energy required to remove successive electrons?

Answer 23

Removal of each
successive electron
requires more energy
• Cation gets smaller and
electrons are held tighter

Question 24

do valence or core electrons in full subshells have more energy? energy required to remove? why the difference?

Answer 24

• Core electrons which are in full subshells
are much lower in energy than the valence
shell electrons
• A lot more energy is required to remove
core electrons compared with valence
electrons
• The large jump in ionization energies
occurs between the removal of valence
electrons and core electrons

Question 25

what happens when a neutral atom gains an electron? what is electron affinity?

Answer 25

• Energy released when a neutral atom gains an electron
to form an anion
• Exothermic reaction
Fundamentally opposite of ionization energy

Question 26

what happens to affinity as we move across rows?

Answer 26

Affinity increases as we move across rows in the
periodic table
• Zeff is larger as we move across a period so there is a
greater attractive force between the added electron and
the nucleus, resulting in more energy being released

Question 27

trends of metallic character? (3 points)

Answer 27

Metals tend to lose electrons in chemical reactions
• As we move across the rows metallic character
decreases
• As we move down groups the metallic character
increases