Chemical Periodicity

Atomic Structure and

Atomic Size– Quantum mechanical model doesn’t

sharply define boundary to limit size– Atomic radius: ½ the distance between

nuclei of 2 like atoms in a diatomic molecule

Atomic radius

• •

Atomic size

Atomic SizeA

tom

ic S

ize I

ncr

easi

ng

Atomic Size Increasing“Fatty Francium”

Octet Rule: atoms want 8 e- in their valence energy level

Ionization Energies: amount of energy required to remove an electron from the valence shell of an atom

Nobel Gases - don’t want to lose e- so they have very high

ionization energyLi - doesn’t take much energy to lose e-, low ionization energyF - wants to gain an e- , therefore takes large amount of energy to pull off an e-, high ionization energy

• Which atom has the larger radius?

–Be or Ba

–Ca or Br

Ba

Ca

Examples

▫As you move down a group the ionization energy decreases b/c of the shielding effect

e- e-

+

e- e-

e-

e- e-

e-

e- e-

e-

Inner e- tend to push outer e- away from the nucleus b/c both have

negative charges

▫As a result of this shielding effect outer e- are less tightly bound to the nucleus than inner e-

Ionization Energy Increase

Ion

izatio

n E

nerg

y Incre

ase

D. Ionization Energy (cont.)

• Ion – positively (cation) or negatively (anion) charged atom, gains or loses electrons

Ionic Size

Cations Increase

Ion

ic S

ize I

ncr

ease

Anions Increase

• Which atom has the higher ionization energy

–N or Bi

–Ba or Ne

N

Examples

Ne

Electronegativity• The electronegativity of an element is the

tendency for the atoms to attract e- when they are chemically combined with another element

• Noble Gases have NO electronegativity b/c they don’t gain e-

• Increase from left to right b/c of octet rule• Decrease when move down a group b/c of

shielding effect

Electronegativity Increase

Ele

ctron

eg

ativity In

crease

E. Electronegativity (cont.)

Periodic Table of the

Elements

Atomic Size Increasing

Ato

mic

Siz

e I

ncr

easi

ng

Ionic Size Increasing

Ion

ic S

ize I

ncr

easi

ng

“Fatty Francium”

Fr

F. Summary of Trends

Ionization Energy Increase

Ion

izatio

n E

nerg

y Incre

ase

Electronegativity Increase

Ele

ctron

eg

ativity In

crease

F

“FriendlyFluorine”

Whiteboard PracticeWhich of these elements has a larger atomic size?

Arrange these elements in order of increasing atomic size.

S, Cl, Al, NaAnswer: Cl, S, Al, NaAnswer: Cl, S, Al, Na

Is this a period trend or a group trend?

Answer: Period trendAnswer: Period trend

1. Li or K2. C or O 4. Ca or K

3. Te or I

White Board PracticeWrite the element with the greatest value for

Ionization Energy.

Rank the sets of atoms from smallest to largest for Electronegativity.

1. Al or P

2. Ca or Ni

3. O or Ne

4. Zr or Cs

1. Se, Cr, Zn Cr, Zn, Se

2. P, Ar, Mg Ar, Mg, P

Atomic Size War!Atomic Size War!• Each card has an element symbol. • You will flip over one card and place it on the table and your

partner will do the same.• Who ever has the Element with the GREATER atomic size Wins

those two elements.• You continue to each flip over cards until one player has all the

elements.• If you flip over the same element you will each turn over one

more card and the player with the greater atomic size will win all four cards.

• Separate the cards and shuffle and play a new game using a different trend.