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

IA IIA IIIA IVA VA VIA VIIA

= 1 Angstrom

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

Periodic Trends in Atomic Radii

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 175

Relative Size of Atoms

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

Attraction and Repulsion of Electrical Charges

+ +

Particles with opposite charges attract

one another.

Particles with like chargesrepel one another.

- -+ -

Coulombic Attraction

1+ 1-

2+ 2-

4- 3-

2+ 2-

Coulombic Attraction

1) Charge opposites attract like repels 2) Distance

A

B

C

D

Shielding Effect

Kernel electrons block the attractive force of the nucleus from the valence electrons

+nucleus

Valence

Electrons--

--

Electron

Shield

“kernel”

electrons

Shielding Effect and Effective Nuclear Charge

+

__

_

Mg = [Ne]3s2

attractionsrepulsions

Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 336

Mg24.305

12

++++++

++

Decreasing Atomic Size Across a Period

• As the attraction between the (+) nucleus and the (–) valence electrons , the atomic size . Greater coulombic attraction.

• From left to right, size decreases because there is an increase in nuclear charge and Effective Nuclear Charge (# protons – # core electrons).

• Each valence electron is pulled by the full ENC

(ENC = 1)

+++

(ENC = 2)

+

Li Be(ENC = 3)

B1s22s1 1s22s2 1s22s22p1

Li Be B

Sizes of ions: electron repulsion

• Valence electrons repel each other.

9 +

• When an atom becomes a anion (adds an electron to its valence shell) the repulsion between valence electrons increases without changing ENC

• Thus, F– is larger than F

Fluorine atomF

1s22s22p5

9+-

--

-

--

--

-

F1-

1s22s22p6

+1e+1e-- 9+-

--

-

--

--

-

-

Fluorine ionFluoride ion

Atomic Radius of Atoms

Na

K

Rb

Cs

ClSPSiAl

BrSeAsGeGa

ITeSbSnIn

Tl Pb Bi

Mg

Ca

Sr

Ba

Be FONCB

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

IA IIA IIIA IVA VA VIA VIIA

= 1 Angstrom

0.60 0.31

0.95 0.65

1.33 0.99

1.48 1.13

1.69 1.35

1.71 1.40 1.36

0.50 1.84 1.81

0.62 1.98 1.85

0.81 2.21 2.16

0.95

IA IIA IIIA IVA VA VIA VIIA

= 1 Angstrom

Li1+ Be2+

Na1+ Mg2+

Ba2+

Sr2+

Ca2+K1+

Rb1+

Cs1+

Cl1-

N3- O2- F1-

S2-

Se2- Br1-

Te2- I1-

Al3+

Ga3+

In3+

Tl3+

Ionic Radii

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

IA IIA IIIA IVA VA VIA VIIA

= 1 Angstrom

He

Ne

Ar

Kr

Xe

Rn

0.93

1.12

1.54

1.69

1.90

2.20

VIIIA

0.60 0.31

0.95 0.65

1.33 0.99

1.48 1.13

1.69 1.35

1.71 1.40 1.36

0.50 1.84 1.81

0.62 1.98 1.85

0.81 2.21 2.16

0.95

IA IIA IIIA IVA VA VIA VIIA

= 1 Angstrom

Li1+ Be2+

Na1+ Mg2+

Ba2+

Sr2+

Ca2+K1+

Rb1+

Cs1+

Cl1-

N3- O2- F1-

S2-

Se2- Br1-

Te2- I1-

Al3+

Ga3+

In3+

Tl3+

Ionic Radii

Trends in Atomic and Ionic Size

152

186

227

Li

Na

K

60

Li+

95

Na+

133

K+

e

e

e

F-

136

Cl-

181

Br-

195

F

Cl

Br

64

99

114

e

e

e

Metals NonmetalsGroup 1

Al

143

50

ee

e

Group 13 Group 17

Cations are smaller than parent atoms Anions are larger than parent atoms

Al3+

152

Li

60

Li+

e

152

60

Li+

e

e

e

e

Li

Lithium atom

Lithium ion

+

152

Li

Lithium atom

Li

Energy

IA IIA IIIA IVA VA VIA VIIA

0.60 0.31

0.95 0.65

1.33 0.99

1.48 1.13

1.69 1.35

1.71 1.40 1.36

0.50 1.84 1.81

0.62 1.98 1.85

0.81 2.21 2.16

0.95

Li1+ Be2+

Na1+ Mg2+

Cl1-

N3- O2- F1-

S2-

Se2- Br1-

Te2- I1-

Al3+

Ga3+

In3+

Tl3+

Ca2+K1+

Sr2+Rb1+

Cs1+ Ba2+

Li

Na

K

Rb

Cs

ClSPSiAl

BrSeAsGeGa

ITeSbSnIn

Tl Pb Bi

Mg

Ca

Sr

Ba

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

Be B C N O F

= 1 Angstrom

AtomicRadii

IonicRadii

Cations: smaller than parent atoms

Anions: LARGERthan parent atoms

The Octet Rule and Common Ions

Oxygen atomO

1s22s22p4

Fluorine atomF

1s22s22p5

Sodium atomNa

1s22s22p63s1

Magnesium atomMg

1s22s22p63s2

8+-

--

-

- --

-9+-

--

-

--

--

-

11+-

--

-

-

--

--

-

-

12+-

--

-

-

--

--

--

-

11+-

--

-

-

--

--

-

12+-

--

-

-

--

--

-

Oxygen ionO2-

1s22s22p6

Fluorine ionF1-

1s22s22p6

Sodium ionNa1+

1s22s22p6

Magnesium ionMg2+

1s22s22p6

10+-

--

-

-

--

--

-

Neon atomNe

1s22s22p6

+1e+1e-- -1e-1e-- -2e-2e--+2e+2e--

8+-

--

-

- --

-

-

-9+-

--

-

--

--

-

-

Isoelectronic Species

11+-

--

-

-

--

--

-

12+-

--

-

-

--

--

-

Oxygen ionO2-

1s22s22p6

Fluorine ionF1-

1s22s22p6

Sodium ionNa1+

1s22s22p6

Magnesium ionMg2+

1s22s22p6

8+-

--

-

- --

-

-

-9+-

--

-

--

--

-

- 10+-

--

-

-

--

--

-

Neon atomNe

1s22s22p6

IsoelectronicIsoelectronic - all species have the same number of electrons.

Can you come up with another isoelectronic series of five elements?

p = 8n = 8e = 10

p = 9n = 9e = 10

p = 10n = 10e = 10

p = 11n = 11e = 10

p = 12n = 12e = 10

Lewis Structure

Na ClX

o o

o o

ooo H C No

XX

X

X

ClNa H C N

ClNa H C N

Gilbert Lewis

“Lewis Dot Notation”

Atomic Radius vs. Atomic Number

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