Periodic table trends

Alternative periodic tables

Dutch Periodic Table

106

107

108

109

110

111

112

113

114

115

116

117
118

Strong, Journal of Chemical Education, Sept. 1989, page 743

Benfey’s Periodic Table

Dmitri Mendeleev

• Russian
• Considered the “Father” of the

periodic table

• Arranged elements by atomic

mass and in columns based
on properties.

• Predicted existence of several

unknown elements

1869 table

Modern Periodic Table

• Henry G.J. Moseley
• bombarded elements

with X-rays (1914).

• Determined the atomic

number for each
element.

• Arranged elements by

increasing atomic
number

1887 - 1915

Modern Periodic Law: When elements are
arranged in order of increasing atomic number,
their physical and chemical properties show a
periodic pattern.

The Periodic Table

On your periodic table, draw the “staircase”

starting from Boron.

1
IA

18

VIIIA

1
1
H

1.00797

2
IIA
Periodic Table

13
IIIA

14
IVA

15
VA

16
VIA

17

VIIA

2

He
4.0026

2
3
Li
6.939

4

Be
9.0122

5
B

10.811

6
C

12.0112

7
N

14.0067

8
O

15.9994

9
F

18.9984

10
Ne
20.179

3
11
Na

22.9898

12
Mg
24.305

3

IIIB

4

IVB

5
VB

6

VIB

7

VIIB

8

9

VIIIB

10

11
IB

12
IIB

13
Al

26.9815

14
Si

28.086

15
P

30.9738

16
S

32.064

17
Cl

35.453

18
Ar
39.948

4
19
K

39.102

20
Ca
40.08

21
Sc
44.956

22
Ti
47.90

23
V

50.942

24
Cr
51.996

25
Mn
54.9380

26
Fe
55.847

27
Co

58.9332

28
Ni
58.71

29
Cu
63.54

30
Zn
65.37

31
Ga
65.37

32
Ge
72.59

33
As

74.9216

34
Se
78.96

35
Br
79.909

36
Kr
83.80

5
37
Rb
85.47

38
Sr
87.62

39
Y

88.905

40
Zr
91.22

41
Nb
92.906

42
Mo
95.94

43
Tc
[99]

44
Ru
101.07

45
Rh

102.905

46
Pd
106.4

47
Ag

107.870

48
Cd
112.40

49
In

114.82

50
Sn
118.69

51
Sb
121.75

52
Te
127.60

53
I

126.904

54
Xe
131.30

6
55
Cs

132.905

56
Ba
137.34

57
La
138.91

72
Hf
178.49

73
Ta

180.948

74
W

183.85

75
Re
186.2

76
Os
190.2

77
Ir
192.2

78
Pt

195.09

79
Au

196.967

80
Hg
200.59

81
Tl

204.37

82
Pb
207.19

83
Bi

208.980

84
Po
[210]

85
At
[210]

86
Rn
[222]

7
87
Fr
[223]

88
Ra
[226]

89
Ac
[227]

104
Ku
[260]

105

106

107

108

109

http://www.chemsoc.org/viselements/pages/periodic_table.html

Periodic Table: Metallic arrangement

• Layout of the Periodic Table: Metals vs.

nonmetals

1
IA

18

VIIIA

1
2
IIA

13
IIIA

14
IVA

15
VA

16
VIA

17

VIIA

2

3
3

IIIB

4

IVB

5
VB

6

VIB

7

VIIB

8

9

VIIIB

10

11
IB

12
IIB

4

5

6

7

Metals

Nonmetals

•

Metals (left of “staircase” except H)

about 75% of all the elements

•

- Good conductors of electricity and heat
- Ductile (can be pulled into wires)
- Malleable (hand be hammered into shapes)
- Lustrous (shiny)
- In chemical reactions, metals lose electrons to form positively

charged ions

- All are solids except for mercury, which is a liquid at room

temperature

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Metals and nonmetals

• Nonmetals

(right of “staircase”)

- Poor conductors of heat and electricity
- Not lustrous
- Can be gases, liquids, or solids
- Solid nonmetals are brittle
- Tend to gain electrons in reactions with metals

to form negatively charged ions

- Share electrons in reactions with other

nonmetals

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Metalloids or semi-metals

• The elements that lie close to the “stair-step”

line
– B, Si, Ge, As, Sb, Te, Po, At

-Possess some
characteristics of
metals/some of nonmetals

• Groups or families

• The columns of the periodic table
• Within each column, elements have similar chemical
And physical properties.
• Same # of valence electrons

Columns of the periodic table

Groups/
Families

• 1 – Alkali metals
• 2 – Alkaline Earth metals
• 3-12 – Transition metals
• 17 – Halogens
• 18 – Noble gases

The alkali metals (Group 1)

- Lithium through francium.

- react with nonmetals to become ions with a +1
charge.
- the most reactive metals on the periodic table

Chemistry of the Groups

H

1

Li

3

Na

11

K

19

Rb

37

Cs

55

Fr

87

1

Chemistry of the Groups

• The alkaline earth metals (Group 2)

• Become ions with a +2 charge

•
•

Copyright 2007 Pearson Benjamin Cummings. All rights reserved.

Be

4

Ca

20

Sr

38

Ba

56

Ra

88

Mg

12

2

The halogens (Group 17)

- Become ions with a −1 charge.
- the most reactive non-metals on the periodic table

Chemistry of the Groups

F

9

Cl

17

Br

35

I

53

At

85

17

The noble gases (Group 18)

- Helium (He) through radon (Rn);

- are monatomic (each atom remains alone - does not bond

with other atoms)

- are inert (unreactive) gases at room temperature and

pressure

Chemistry of the Groups

He

2

Ne

10

Ar

18

Kr

36

Xe

54

Rn

86

18

Rows of the Periodic Table

•

Periods

:

(rows 1

-

7)

•

These elements’ valence electrons are in

the same principal energy levels.

1
IA

18

VIIIA

1
2
IIA

13
IIIA

14
IVA

15
VA

16
VIA

17

VIIA

2

3
3

IIIB

4

IVB

5
VB

6

VIB

7

VIIB

8

9

VIIIB

10

11
IB

12
IIB

4

5

6

7

2nd Period

6th Period

THE OCTET RULE

• ATOMS TEND TO GAIN, LOSE, OR SHARE

ELECTRONS IN ORDER TO ACQUIRE A
FULL SET OF VALENCE ELECTRONS.
– (8 for all except H and He, which are 2)

• Metals lose valence electrons to gain a full

set in the previous energy level.

• Nonmetals gain valence electrons to gain a

full set on the SAME energy level

General Periodic Trends

•

Atomic and ionic size

•

Ionization energy

•

electronegativity

Periodic trends:

Atomic size/radius -
• Distance from the center of an atoms

nucleus to the valence shell

Atomic Radii within a Group

Lithium: 3 protons, energy level 2

Sodium: 11 protons, energy level 3

++ +

e-
2e-

8e-
2e-

++++

e-

+

e-

Hydrogen: 1 proton, energy level 1

*** Atomic Radii increases
going DOWN a group.

General Periodic Trends

Going down a group:
• Valence electrons are in Higher energy levels,
meaning they are farther away from the nucleus.

•More shielding effect from core electrons.

•Shielding effect: core electrons “Shield” outer
electrons from the pull of the positive nucleus.

• electrons are not held as tightly to the nucleus.

Shielding Effect

Core electrons block the

attractive force of the
nucleus from the
valence electrons

+

nucleus

Valence

Electrons-
-

- -

Electron

Shield

“Core” (inner)

electrons

Valence
electrons are
LESS attracted
to nucleus.

Lithium: 3 protons
energy level 2

++ +

e-

2e-

Beryllium: 4 protons,
Energy level 2

Boron: 5 protons,
Energy level 2

+
++

e-

2e-
e-

+

+
++

e-
2e-

e-

e-

++

decreasing

** Atomic radii
DECREASES going
from left to right
across a period.

Atomic radii across a period

General Periodic Trends

•Going from left to right across a period…

• There are MORE protons, so nucleus has a

more POSITIVE charge.

•Electrons held tighter to nucleus.

Lithium
Beryllium

Boron

++ +

e-
2e-

e-

e-

++

If protons were light bulbs….and electrons were moths…...

B

e-
e-

e-

Be

e-
e-

Li

e-

++ +

e-

2e-

+
+

+

e-

2e-
e-

+

Atomic Size / Atomic Radius

• Why does atomic size increase as you move

down the periodic table?
– Because the valence electrons are in principal

energy levels that are FARTHER from the
nucleus.

• Why does the atomic size decrease as you

move across the periodic table from left to
right?
– Because the number of protons increases,

pulling the electrons closer to the nucleus.

Check for Understanding

Ion Sizes: cations (positive)

• An atom becomes SMALLER when it becomes

a cation

• Electrons are MORE attracted to the nucleus

and have

• Less charge repulsion between electrons.

Li: 152 pm

3 e

-

, 3 protons

Li+: 78 pm
2 e-, 3 protons

+

Forming a

cation.

Ion Sizes: anions (negative)

• Atoms become BIGGER when they

become an anion

• Electrons not held as tightly to the nucleus

so size INCREASES.

• Also, more charge repulsion between

electrons.

Forming

an anion.

F: 71 pm
9e-and 9 protons

F- : 133 pm
10 e-and 9 protons

-

Electronegativity

• Definition:

– ability to attract electrons in a chemical bond.
– Ranges from 0.7 to 4 (no units)

• Electronegativity generally increases from

left to right and bottom to top.

• Fluorine is the most electronegative atom -

(it REALLY wants to get more electrons)

Electronegativity

Electronegativity trend

Why does electron attraction increase L to R?

•

Elements on the right (Halogens) need

Only 1 more electron to complete their
Valence shell.

Electronegativity trend

Why does electron attraction decrease top to
bottom?

•

Elements at the bottom have valence
electrons that are less attracted to the
nucleus.
•

Due to additional energy shells

Ionization Energy

• Amount of energy needed to remove a

valence electron from an atom.

• The lower the ionization energy, the easier it

is to remove the electron

• 1stionization energy = remove 1 electron
• 2ndionization energy = remove a 2ndelectron

(etc…)
– Example: Mg

1stIE: 737 kJ
2ndIE: 1450 kJ
3rdIE: 7732 kJ

ionization energy

At

I

Br

Cl

Po

Te

Se

S

Bi

Sb

As

P

Pb

Sn

Ge

Si

F

O

N

Tl

Na

Cs

Rb

K

Ba

Mg

Sr

Ca

In

Ga

Al

H

Li

Be

B

C

** Ionization energy increases from Left to
right and from bottom to top. INCLUDES
noble gases.

First Ionization Energy

++ +

e-

Lithium

8e-

Sodium

2e-

2e-

++++

e-

+

Hydrogen

e-

increasing

Valence electrons are
harder to remove as
they get closer to the
nucleus

Ionization energy is
higher at the top.

Lithium 3 protons

++ +

e-

2e-

Beryllium 4 protons

Boron 5 protons

+
++

e-
2e-
e-

+

++ +

e-
2e-

e-

e-

++

IE is higher to the right:

- Greater electronegativity to the right

(elements need electrons for octet rule)

Natural states of the elements

• Some elements are found by themselves,

uncombined with other elements in nature –
they are monoatomic:
– Noble Metals: Gold, silver, and platinum –

relatively unreactive

– Noble gases

Diatomic Elements

H2

N2 O2 F2

Cl2

Br2

I2

Tl

At

S

Li

Na

K

Fr

Be

Mg

Ca

Ra

Sc

Ac

He

Ne

Ar

Kr

Rn

Ti

V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se

Rb Sr

Y

Xe

Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te

Cs Ba La Hf Ta W Re Os Ir

Pt Au Hg

Pb Bi Po

Al Si

P

B

C

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa U

Np Pu Am Cm Bk Cf Es Fm Md No Lr

S

Tl

Definition: molecules made
up of two atoms of the
same element

At

Trend summary

Traveling from bottom to top and from left to

right

• Decreasing:

– Atom size & ion size

• Increasing:

– Ionization energy
– Electronegativity