Periodic Trends

• There are several important atomic characteristics that show predictable trends that you should know:

–Atomic Size–Ionization Energy–Electron Affinity–Electronegativity

Atomic Size

The bonding atomic radius is defined as one-half of the distance between bonded nuclei.

++++++

++

Decreasing Atomic SizeAcross a Period

• The effect is that the more positive nucleus (+) has a greater pull on the electron cloud (-)

• The increased attraction pulls the cloud in, making atoms smaller as we move from left to right across a period

+++ +

Li Be B1s22s1 1s22s2 1s22s22p1

Li Be B

Relative Size of Atoms

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 350

Li

Na

K

Rb

Cs

La

XeKr

Zn

Cl

FHe

H

3dtransition

series

4dtransition

series

0.3

0.25

0.2

0.15

0.1

0.05

00 10 20 30 40 50 60

atomic number

atom

ic r

adiu

s

Atomic Radii

Li

Na

K

Rb

Cs

ClSPSiAl

BrSeAsGeGa

ITeSbSnIn

Tl Pb Bi

Mg

Ca

Sr

Ba

Be FONCB

1.52 1.11

1.86 1.60

2.31 1.97

2.44 2.15

2.62 2.17

0.88 0.77 0.70 0.66 0.64

1.43 1.17 1.10 1.04 0.99

1.22 1.22 1.21 1.17 1.14

1.62 1.40 1.41 1.37 1.33

1.71 1.75 1.46

1 2 13 14 15 16 17

INC

RE

AS

ES

INCREASES

Ionization EnergyAmount of energy required to remove an electron

from the ground state of a gaseous atom or ion.

Given enough energy (in the form of a photon) an electron can leave the atom completely.

The number of protons and electrons is no longer equal

IONS!!!

Ionization Energy

• Generally, as one goes across a row, it gets harder to remove an electron.

• The larger the atom is, the easier its electrons are to remove.

• Ionization energy and atomic radius are inversely proportional

Ions

• Here is a simple way to remember which is the cation and which the anion:

This is a cat-ion.This is Ann Ion.

Cats are “paw-sitive”She’s unhappy and negative.

+ +

Sizes of Ions

• Cations are smaller than their parent atoms.– The outermost

electron is removed and repulsions are reduced.

Sizes of Ions

• Anions are larger than their parent atoms.– Electrons are

added and repulsions are increased.

Ionization EnergiesP

erio

d

Group 1 18

1

2

3

4

5

6

1

2

3

4

5

6

7

Be

900

Al

578

Si

787

Ti

659

V

651

Cr

653

Mn

717

Fe

762

Co

760

Ni

737

Cu

746

Zn

906

Ga

579

Ge

762

Nb

652

Mo

684

Tc

702

Ag

731

Cd

868

In

558

Sn

709

Sb

834

Ta

761

W

770

Re

760

Hg

1007

Tl

589

Pb

716

Bi

703

N

1402

O

1314

F

1681

Cl

1251

C

1086

S

1000

Br

1140

I

1008

Na

496

K

419

Rb

403

Cs

376

Ba

503

Fr

--

Ra

509

H

1312

B

801

P

1012

As

947

Se

941

Ru

710

Rh

720

Pd

804

Te

869

Os

839

Ir

878

Pt

868

Au

890

Po

812

At

--

Li

520

Ca

590

Sc

633

Sr

550

Y

600

Zr

640

Hf

659

Mg

738

La

538

Ac

490

2

3 4 5 6 7 11 12

13 14 15 16 17

9

Ne

2081

Ar

1521

Kr

1351

Xe

1170

Rn

1038

He

2372

Rf

--

Db

--

Sg

--

Bh

--

Hs

--

Mt

--

Ds

--

Uub

--

Uut

--

Uuq

--

Uup

--

Uuu

--

Uuo

--

Mg

738

Symbol

First Ionization Energy (kJ/mol)

8 10

INCREASES

DE

CR

EA

SE

S

Electron Affinity

Electron affinity = “Love” of electrons

Energy change accompanying addition of electron to gaseous atom:

Cl + e− Cl−

Electronegativity

• Electronegativity is a measure of an atom’s attraction for another atom’s electrons.

• Is directly related to Electron Affinity

• scale that ranges from 0 to 4.– Fluorine is the most electronegative!!!!

`1

2

3

4

5

6

1

2

3

4

5

6

Electron Affinity & Electronegativity

7

Be

1.5

Al

1.5

Si

1.8

Ti

1.5

V

1.6

Cr

1.6

Mn

1.5

Fe

1.8

Co

1.8

Ni

1.8

Cu

1.9

Zn

1.7

Ga

1.6

Ge

1.8

Nb

1.6

Mo

1.8

Tc

1.9

Ag

1.9

Cd

1.7

In

1.7

Sn

1.8

Sb

1.9

Ta

1.5

W

1.7

Re

1.9

Hg

1.9

Tl

1.8

Pb

1.8

Bi

1.9

1.5 - 1.9

N

3.0

O

3.5

F

4.0

Cl

3.0

3.0 - 4.0

C

2.5

S

2.5

Br

2.8

I

2.5

2.5 - 2.9

Na

0.9

K

0.8

Rb

0.8

Cs

0.7

Ba

0.9

Fr

0.7

Ra

0.9

Below 1.0

H

2.1

B

2.0

P

2.1

As

2.0

Se

2.4

Ru

2.2

Rh

2.2

Pd

2.2

Te

2.1

Os

2.2

Ir

2.2

Pt

2.2

Au

2.4

Po

2.0

At

2.2

2.0 - 2.4

Per

iod

Actinides: 1.3 - 1.5

Li

1.0

Ca

1.0

Sc

1.3

Sr

1.0

Y

1.2

Zr

1.4

Hf

1.3

Mg

1.2

La

1.1

Ac

1.1

1.0 - 1.4Lanthanides: 1.1 - 1.3

1A

2A

3B 4B 5B 6B 7B 1B 2B

3A 4A 5A 6A 7A

8AINCREASES

DE

CR

EA

SE

S

Electronegativity

• Atomic Radii - size

• Ionization Energy – energy change when losing an e-

• Electron Affinity - energy change when gaining an e-

• Electronegativity – ability to attract e- when in a compound

Periodic Trends

Formscation!

Formsanion!

Summary of Periodic Trends

Ionic size (cations) Ionic size (anions)decreases decreases

Atomic radius decreasesIonization energy increasesElectron affinity increasesElectronegativity increases

Ato

mic

rad

ius

incr

ease

sIo

niz

atio

n e

ner

gy

dec

reas

esE

lect

ron

Aff

init

y d

ecre

ases

Ele

ctro

neg

ativ

ity

dec

reas

es

1A

2A 3A 4A 5A 6A 7A

0

CHEMISTRY 12/5/13

“Always remember that you are absolutely unique. Just like everyone else.” – Margaret Mead

DO NOW:

1.In your notes: Which atom has a larger atomic radius:

AGENDA:

1.Move seats

2.Students will be able to remember characteristics of the periodic table by completing a coloring activity

HOMEWORK:

Extra credit: Due before winter break: Bring 1 box of tissue or one hand sanitizer (worth 5 pts extra credit)

• What ion will be formed when K loses 1 e-?

K1+ (cation) • What ion will be formed when O

gains 2 e-?O2- (anion)

• Which ion above is more electronegative?

O2- (anion)