periodic properties of elements (7.1-7.5)

Question 1

What is periodicity?

Answer 1

Repetitive pattern of a property of the elements based on the atomic number.

Question 2

What are periodic properties?

Answer 2

• size of atom & ions (chemical properties)
• ionization energy
• electron affinity

Question 3

Effective Nuclear Charge

Answer 3

the nuclear charge reduced by screening of core electrons. valence electrons are screened from the full nuclear charge by the inner core electrons. it increases across a period, drops with a start of a new shell.

• Z(eff)= Z(atomic number)-S( a screening constant)

Question 4

anions

Answer 4

larger than their neutral parent atoms: electrons are added and repulsion’s between atoms are increased

Question 5

isoelectric series

Answer 5

ions have the same number or electrons, ionic size decreases with an increasing nuclear charge,

Question 6

ionization energy

Answer 6

• is the energy required to remove an electron from an atom
• the higher the ionization energy, the more difficult it is to remove an electron

Question 7

first ionization energy

Answer 7

`energy is required to remove the first electron

Na -> Na+ + e-

Question 8

second ionization energy

Answer 8

energy required to remove the second electron

Na+ -> Na2+ +e-

Question 9

periodic trends in first ionization energy (I 1)

Answer 9

• generally increases across a period
• generally decreases down a group

(opposite the trend of atomic size)
(lower ionization energy= higher reactivity)

Question 10

factors that influence ionization energy

Answer 10

• increase with effective nuclear charge (across period)
• larger atoms have lower ionization energies (down groups)
• big drop between closed- shell noble gasses
• nitrogen is harder to break half filled shell
• oxygen is easier to form half filled shells

Question 11

electron affinity

Answer 11

is the energy change accomplish the addition of an electron to gaseous atom
- not much change in a group, across a period it becomes larger in magnitude.

Cl + e- -> Cl-

typically exothermic is for most elements, it is negative

Question 12

exceptions for electron affinity

Answer 12

1. Group 2A: s subshell is full
2. Group 8A: p subshell is full

these have positive or small negative electron affinities
3. Group 5A: p subshell is half full

nitrogen- no stable anion

Question 13

Periodic trends in atomic size, ionization energies & electron affinities, electron affinities apply to the ATOMS of the elements