Periodic Trends We will explain observed trends in Atomic (and Ionic) Radius Ionization Eenergy Electronegativity size lose e – attract e – nuclear.

Periodic Trends• We will explain observed trends in

Atomic (and Ionic) Radius

Ionization Eenergy

Electronegativity

size

lose e–

attract e–

nuclear charge & shieldingexplained by:

(protons) & (levels)

inner e– levels block nuclear charge

down a group

Nuclear Charge & Shielding

shielding:

nuclear charge: protons(+) attracting e–’s(–)

+3

+11

+10

+18

Li across a period

Na

Ne

Ar

What happens to atomic radius?

decreases

increases

WHY?

Atomic Radius

-more levels of

shielding(less

attraction)

increases d

ow

n g

rou

p

-more nuclear charge(more attraction)

decreases across period

Cations from metals:e–’s removedpositive (+) chargesmallerouter shell lost

Anions from nonmetals:e–’s addednegative (–) charge largermore e– repulsions

Ions & Ionic Radius

decreases d

ow

n a g

rou

p

-more levels of

shielding(less

attraction)

-more nuclear charge(more attraction)

increases across period

Ionization Energy (IE):•energy required to remove an e– +

Electronegativity (EN) Trends • atom’s ability to attract bonded electrons

decreases d

ow

n g

rou

pincreases across period

-more levels of

shielding(less

attraction)

-more nuclear charge(more attraction)

Periodic Trends (Summary)

so…Atomic Radius __________

so…E

lectron

egativity _________

so…Ionization Energy _________

so…Electronegativity _________

so…Io

nizatio

n E

nerg

y _________

so…A

tom

ic Rad

ius __________

nuclear chargeshielding

All explained by ATTRACTION:

ATTRACTION INcreases AT

TR

AC

TIO

N D

Ecreases

decreases

increases

increases

decreases

decreases

increases

1. Atoms get ________ down a ________.

A. bigger, period

B. smaller, group

C. bigger, group

D. smaller, period

Quick Quiz!

WHY?

more energy levelsmore shieldingless attraction

2. Atomic radii _________ across a period?

A. atoms get bigger

B. atoms get smaller

C. atoms stay the same size

D. atoms

WHY?

more protonsmore nuclear charge

more attraction

Quick Quiz.

3. Which of the following correctly orders atomic size from largest to smallest?

A. F > Cl > Br

B. Li > Na > K

C. F > N > B

D. Mg > Al > S

Quick Quiz.

4. Metals tend to ________ electrons to form _________ cations.

A. gain, positive

B. gain, negative

C. lose, negative

D. lose, positive

Quick Quiz.

5. As you go across period 3 from Mg to Cl, the energy needed to remove an electron from an atom ______________.

A. generally increases

B. generally decreases

C. does not change

D. varies unpredictably.

Quick Quiz.

WHY?

more protonsmore nuclear charge

more attraction(same energy level/shielding)

6. Which of the following is the most electronegative?

A. Cl

B. Se

C. Na

D. I

Quick Quiz.

7. The noble gases have _____________.

A. high ionization energies.

B. high electronegativities.

C. large atomic radii.

D. a tendency to form both cations and anions.

Quick Quiz.

8. Alkali metals have lower ionization energies than halogens because _______________.

A. alkali metals are smaller with more protons.

B. halogens are larger with more protons.

C. alkali metals are larger with lower nuclear charges.

D. halogens are smaller with fewer protons.

Quick Quiz.

9. Fluorine is the most electronegative halogen because it is ___________________.

A. larger with more energy levels (shielding)

B. smaller with more energy levels (shielding)

C. smaller with fewer energy levels (shielding)

D. larger with fewer energy levels (shielding)

Quick Quiz.