Periodic Properties

■ Atomic & Ionic Radius

■  Ionization Energy

■ Electron Affinity

☛ We want to understand the variations in these properties in terms of electron configurations.

The Periodic Table

■ Elements in a column of the periodic table have very similar electron configurations.

■ Elements in a column of the periodic table also have similar chemical properties.

➡ Valence electrons determine the chemical behavior of an atom.

Valence Electrons

■ Valence electrons are those with the highest n value, plus any in partially filled d or f shells.

■ These electrons are the farthest from the nucleus, and they have the highest energies. Thus they are the most “accessible” to other atoms.

Can you explain this graph?

Valence Electrons■ Valence electrons are those with the

highest n value, plus any in partially filled d or f shells.

■ These electrons are the farthest from the nucleus, and they have the highest energies. Thus they are the most “accessible” to other atoms.

☛ Valence electrons determine the chemical properties of an atom.

Paramagnetism■ Electrons have magnetic properties.■ Two electrons with opposite spins have

opposite magnetic properties, so they “cancel out” each other’s magnetism.

■ Atoms with unpaired electrons are attracted or repelled by magnetic fields, and are said to be “paramagnetic.”

■ This is a way to “verify” e– configuration.

Atomic Radius

■ Size of an atom is determined mainly by valence electrons. (Why?)

■ Hard to define and measure■ Which would you expect to be larger:

Na or K? N or F?

Atomic Radius Variations

■ Moving across a row, Z increases while valence electrons are added to the same n-shell → size decreases

■ Moving down a column, the n quantum number of the valence electrons increases → size increases

Atomic Radius

Variations

Ionic Radii

■ Think about these the same way as for atoms: electron configurations.

■ Be sure to use correct # of electrons.■ Which should be larger:

Mg or Mg2+? F or F–?

Ionic Radii

■ Anions are always bigger than the corresponding neutral atom.

■ Cations are always smaller than the corresponding neutral atom.

■ For isoelectronic ions, the larger the nuclear charge, the smaller the ion.

Ionization Energy■  IE = amount of energy needed to

remove an electron from a free neutral atom.

Z + energy → Z+ + e–

■ Easy to measure (experiment similar to photoelectric effect)

■ Tell us the relative stabilities of different orbitals

Ionization Energy

■ How would you expect IE to vary as you go down a column of the Periodic Table?

■  ... as you go across a row?■ Why?

Ionization Energies■  IE decreases going down a column of

the periodic table.■  IE increases going across a row of the

periodic table.■ Some exceptions:➡ Filled shells or subshells are especially

stable.➡ Half-filled subshells are also fairly

stable.

Ionization Energies

Ionization Energies

Can you explain the general trends and the variations?

kJ/m

ol

Ionization Energies

Again?

kJ/m

ol

Again?

Higher Ionization Energies

■ Can also define and measure higher IE’s:2nd IE:

Z+ + energy → Z2+ + e–

■ Can predict and understand these based on electron configuration of the ions involved.

2nd Ionization Energies

1st IonizationEnergy

Li Be B C N O F Ne NaMg Al Si P S Cl Ar K0

500100015002000250030003500400045005000

1st IonizationEnergy

2nd IonizationEnergy

Transition���Metals - some complications

kJ/m

ol

Ionization Energies

Electron Attachment Enthalpy (Affinity)

■ Measures atom’s tendency to form anions■ EA = energy released upon adding an

electron to a neutral atom,Z(g) + e– → Z– (g) + energy (=EA)

■ Older books called this the electron affinity, but is now called the Electron Attachment Enthalpy. This is opposite in sign from old definition.

■ Note: EA can be positive or negative

Electron Affinity

■  If EA is negative, the atom “wants” to add an electron and form an anion.

■  If EA is positive, the atom does not “want” to add an electron to form an anion. i.e., the anion is unstable.

■ Which elements will have the most negative EA’s? Why?

Periodic Table: ���Metals & Non-metals

■ What makes an element a metal or a non-metal?

Properties? Electron configuration?

■ How are metals & non-metals grouped in the periodic table?

Comments on the Periodic Table

Lanthanide series

Actinide series

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

140.1

581.1

140.9

59

144.2

60

(145)

61

150.4

62

152.0

63

157.2

64

158.9

65

162.5

66

164.9

67

167.3

68

168.9

69

173.0

70

175.0

711.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.0 1.2

232.0

901.2

231.0

911.3

238.0

921.5

(237)

931.3

(244)

94

(243)

95

(247)

96

(247)

97

(251)

98

(252)

99

(257)

100

(258)

101

(259)

102

(260)

1031.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.5

H

Li

Na

K

Rb

Cs

Fr

Be

Mg

Ca

Sr

Ba

Ra

Sc

Y

Ti

Zr

Hf

V

Nb

Ta

Cr

Mo

W

Mn

Tc

Re

Fe

Ru

Os

Co

Rh

Ir

Ni

Pd

Pt

Cu

Ag

Au

Zn

Cd

Hg

B

Al

Ga

In

Tl

C

Si

Ge

Sn

Pb

N

P

As

Sb

Bi

O

S

Se

Te

Po

F

Cl

Br

I

At

Ne

Ar

Kr

Xe

Rn

He

UnqUnpUnhUnsAc

1.008

12.1

6.941

31.0

22.99

111.0

39.10

190.9

85.47

370.9

132.9

550.8

(223)

870.8

9.012

41.5

24.30

121.2

40.08

201.0

87.62

381.0

137.3

561.0

(226)

881.0

44.96

211.3

88.91

391.2

138.9

571.1

(227)

891.1

47.88

221.4

91.22

401.3

178.5

721.3

104

50.94

231.5

92.91

411.5

180.9

731.4

1052.1

52.00

241.6

95.94

421.6

183.8

741.5

106

54.94

251.6

(98)

431.7

186.2

751.7

107

55.85

261.7

101.1

441.8

190.2

761.9

58.93

271.7

102.9

451.8

192.2

771.9

58.69

281.8

106.4

461.8

195.1

781.8

63.55

291.8

107.9

471.6

197.0

791.9

65.39

301.6

112.4

481.6

200.6

801.7

10.81

52.0

26.98

131.5

69.72

311.7

114.8

491.6

204.4

811.6

12.01

62.5

28.09

141.8

72.61

321.9

118.7

501.8

207.2

821.7

14.01

73.0

30.97

152.1

74.92

332.1

121.8

511.9

209.0

831.8

16.00

83.5

32.07

162.5

78.96

342.4

127.6

522.1

(209)

841.9

19.00

94.0

35.45

173.0

79.90

352.8

126.9

532.5

(210)

852.1

20.18

10

39.95

18

83.80

36

131.3

54

(222)

86

4.003

2

(261) (262) (263) (262)

La

Zintl Line(fuzzy)

Metals

Nonmetals