MODERN ATOMIC THEORY

Chapter 10

ANCIENT GREEKS’ VIEW OF MATTER

About 400 B.C. , Aristotle thought all matter was made of four “elements” :

• earth

• air

• fire

• water

ANCIENT GREEKS’ VIEW OF MATTER

At about the same time another Greek philosopher, Democritus, said that matter was made of tiny, indivisible particles called atoms.

Atomos is the Greek word for indivisible.

Modern View of the Atom

Tiny, dense, positively charged nucleus made up of positive protons and neutral neutrons.

Negatively charged electron shells enclose the nucleus and contain negative electrons.

Atomic Spectra and BohrAtomic Spectra and Bohr

1. Any orbit should be possible and so is any energy.

2. But a charged particle moving in an electric field should emit energy.

End result should be destruction!

+Electronorbit

One view of atomic structure in early 20th century was that an electron (e-) traveled about the nucleus in an orbit.

Similarity of Elements

Elements are grouped together in vertical columns (Groups) that have similar properties.

Alkali Metals -- Li, Na, K, Rb, & Cs

Halogens -- F2, Cl2, Br2, & I2

Noble Gases -- He, Ne, Ar, Kr, Xe, & Rn

Electromagnetic Radiation

Radiant energy that exhibits wave-like behavior and travels through space at the speed of light in a vacuum.

Electromagnetic RadiationElectromagnetic Radiation

wavelengthVisible light

wavelengthUltraviolet radiation

Amplitude

Node

Waves

Waves have 3 primary characteristics:

1. Wavelength: distance between two peaks in a wave.

2. Frequency: number of waves per second that pass a given point in space.

3. Speed: speed of light is 2.9979 108 m/s.

As the wavelength () decreases, the frequency () increases.

The electromagnetic spectrum.

Wavelength and frequency can be interconverted.

= c/ = frequency (s1, Hz, cyc/s, or waves/s )

= wavelength (m)

c = speed of light (m/s)

Huygens thought light travels as waves, while Newtonbelieved it travels as particles.

Photons

Photons -- tiny particle of electromagnetic radiation -- a bundle of light energy.

Ground state -- electrons are at their lowest energy state in an atom.

Excited state -- electrons have absorbed energy by jumping up to a higher energy state in the atom.

Larger energy jumps by electrons produce shorter wavelength (more energetic) light.

Visible lines in H atom spectrum are called the BALMER series.

High EHigh EShort Short High High

Low ELow ELong Long Low Low

Line Spectra of Excited Atoms

Line Spectra of Excited Atoms

Excited atoms emit light of only certain wavelengths

The wavelengths of emitted light depend on the element.

Atomic Spectrum of Hydrogen

Continuous spectrum: Contains all the wavelengths of light.

Bright Line (discrete) spectrum: Contains only some of the wavelengths of light.

The diagrams above present evidence for discrete energy levels about a nucleus. Electrons can only be found in certain energy levels with certain energies.

Atomic Line Spectra and

Niels BohrBohr’s greatest contribution to

science was in building a simple model of the atom. It was based on an understanding of the BRIGHT LINE SPECTRA of excited atoms.

Niels Bohr

(1885-1962)

Bohr’s Model Bohr’s Model Bohr’s Model was incorrect.

Replaced by QUANTUM or WAVE MECHANICS MODEL.

e- can only exist in certain discrete orbitals.

e- is restricted to QUANTIZED energy states.

e- can not be exactly located--location based upon probability.

Quantum or Wave Mechanics

de Broglie (1924) proposed that all moving objects have wave properties.

de Broglie (1924) proposed that all moving objects have wave properties.

L. de Broglie(1892-1987)

Schrodinger applied idea of e- behaving as a wave to the problem of electrons in atoms.

E. Schrodinger1887-1961

Quantum or Wave Mechanics

The Bohr Model of the atom paved the way for the Quantum MechanicalTheory, but current theory is in no way derived from the Bohr Model of the atom. The Bohr Model of the Atom was fundamentally incorrect--atoms do not move in circular orbitsabout the nucleus.

Failure of the Bohr Model

1s Orbital

2s Orbital

p Orbitalsp Orbitals

A p orbital

The three p orbitals lie 90o apart in space

2px Orbital

2py Orbital

2pz Orbital

3px Orbital

3dxy Orbital

3dxz Orbital

3dyz Orbital

3dyz Orbital

3dx2

- y2 Orbital

Quantum Numbers (QN)1. Principal QN (n = 1, 2, 3, . . .) - related to size

and energy of the orbital.

2. Angular Momentum QN -- l (s, p, d, & f) - relates to shape of the orbital.

3. Magnetic QN -- ml (x, y, or z plane) - relates to orientation of the orbital in space relative to other orbitals.

4. Electron Spin QN -- ms (+1/2, 1/2) - relates to the spin states of the electrons-- clockwise or counterclockwise.

Electron Arrangement

Level Sublevel # Orbitals # electrons

1-7 s 1 2

2-7 p 3 6

3-7 d 5 10

4-7 f 7 14

Energy Levels and Orbitals

• n = the number of the energy level.

• n2 = the number of orbitals in an energy level.

• 2n2 = the number of electrons in an energy level.

Pauli Exclusion Principle

In a given atom, no two electrons can have the same set of four quantum numbers (n, l, ml, ms).

Therefore, an orbital can hold only two electrons, and they must have opposite spins.

Aufbau Principle

As protons are added one by one to the nucleus to build up the elements, electrons are similarly added to these hydrogen-like orbitals.

Electron Filling Order

--Aufbau

Hund’s Rule

The lowest energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli principle in a particular set of degenerate orbitals. Orbitals half-fill before they completely fill.

Writing Atomic Electron Configurations

Writing Atomic Electron Configurations

Electron configuration notation Electron configuration notation

11 s

value of nvalue of l

no. ofelectrons

for H, atomic number = 1

Two ways of writing Two ways of writing configs. One is configs. One is called the called the electron electron configuration configuration notation.notation.

Two ways of writing Two ways of writing configs. One is configs. One is called the called the electron electron configuration configuration notation.notation.

Electron-dot symbol is H.

Writing Atomic Electron Configurations

Writing Atomic Electron Configurations

Two ways of Two ways of writing writing configs. Other configs. Other is called the is called the orbital box orbital box notation.notation.

Two ways of Two ways of writing writing configs. Other configs. Other is called the is called the orbital box orbital box notation.notation.

Arrowsdepictelectronspin

ORBITAL BOX NOTATIONfor He, atomic number = 2

1s

21 s

Arrowsdepictelectronspin

ORBITAL BOX NOTATIONfor He, atomic number = 2

1s

21 s

Quantum numbers are an energy address instead of a positional address.Electron-dot symbol is He:

LithiumLithium

Group 1A

Atomic number = 3

1s22s1 ---> 3 total electrons

Li.

1s

2s

3s3p

2p

BerylliumBeryllium

Group 2A

Atomic number = 4

1s22s2 ---> 4 total electrons

Be:

1s

2s

3s3p

2p

BoronBoron

Group 3A

Atomic number = 5

1s2 2s2 2p1 --->

5 total electrons

1s

2s

3s3p

2p

:B.

CarbonCarbonGroup 4A

Atomic number = 6

1s2 2s2 2p2 --->

6 total electrons

Here we see for the first time HUND’S RULE. When placing electrons in a set of orbitals having the same energy, we place them singly as long as possible.1s

2s

3s3p

2p

:C..

NitrogenNitrogen

Group 5A

Atomic number = 7

1s2 2s2 2p3 --->

7 total electrons

1s

2s

3s3p

2p

:..

.N

OxygenOxygen

Group 6A

Atomic number = 8

1s2 2s2 2p4 --->

8 total electrons

1s

2s

3s3p

2p

:O...

.

FluorineFluorine

Group 7A

Atomic number = 9

1s2 2s2 2p5 --->

9 total electrons

1s

2s

3s3p

2p

..

.:F:

NeonNeonGroup 8A

Atomic number = 10

1s2 2s2 2p6 --->

10 total electrons

Note that we have reached the end of the 2nd period, and the 2nd shell is full!

1s

2s

3s3p

2p

..

..:Ne:

Electron Dot Filling Order

12

74 X

63

58

SodiumSodiumGroup 1A

Atomic number = 11

1s2 2s2 2p6 3s1 or

“neon core” + 3s1 Na.

[Ne] 3s1 (uses rare gas notation)

Note that we have begun a new period.

All Group 1A elements have [core]ns1 configurations.

AluminumAluminumGroup 3A

Atomic number = 13

1s2 2s2 2p6 3s2 3p1

[Ne] 3s2 3p1

All Group 3A elements have

[core] ns2 np1

configurations where n is the period number.

1s

2s

3s3p

2p

.

:Al

PhosphorusPhosphorus

All Group 5A elements have

[core ] ns2 np3

configurations where n is the period number.

Group 5A

Atomic number = 15

1s2 2s2 2p6 3s2 3p3

[Ne] 3s2 3p3

1s

2s

3s3p

2p

.

.:P.

CalciumCalcium

Group 2A

Atomic number = 20

1s2 2s2 2p6 3s2 3p6 4s2

[Ar] 4s2

All Group 2A elements have [core]ns2

configurations where n is the period number.

:Ca

Valence Electrons

The electrons in the outermost principle quantum level of an atom.

Inner electrons are called core electrons.

Relationship of Electron Configuration and Region of the

Periodic Table

Green = s block

Yellow = p block

Lt. Blue = d block

Med. Blue = f block

Broad Periodic Table Classifications

Representative Elements (main group): filling s and p orbitals (Na, Al, Ne, O)

Transition Elements: filling d orbitals (Fe, Co, Ni)

Lanthanide and Actinide Series (inner transition elements): filling 4f and 5f orbitals (Eu, Am, Es)

Transition MetalsTransition Metals

All 4th period elements have the configuration [argon] nsx (n - 1)dy and so are “d-block” elements.

CopperIronChromium

Transition Element Configurations

3d orbitals used for Sc - Zn

3d orbitals used for Sc - Zn

Lanthanides and ActinidesLanthanides and Actinides

All these elements have the configuration [core] nsx (n - 1)dy (n - 2)fz and so are “f-block” elements.

Cerium[Xe] 6s2 5d1 4f1

Uranium[Rn] 7s2 6d1 5f3

Lanthanide Element Configurations

4f orbitals used for Ce - Lu and 5f for Th - Lr

4f orbitals used for Ce - Lu and 5f for Th - Lr

Properties of Metals• malleable

• ductile

• good conductors of heat & electricity

• tend to lose electrons--oxidation

• left of zigzag line on periodic table

• most active metal in lower left corner (Fr)

Properties of Nonmetals• not malleable or ductile

• brittle

• nonconductors of heat & electricity

• tend to gain electrons -- reduction

• right of zigzag line on periodic table

• most active nonmetal in upper right corner (F)

Properties of Metalloids

• properties intermediate between metals and nonmetals

• found bordering zigzag line on periodic table

• B, Si, Ge, As, Sb, & Te

ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY

General Periodic Trends

Higher Z*.Electrons heldmore tightly.

Larger orbitals.Electrons held lesstightly.

Higher Z*.Electrons heldmore tightly.

Larger orbitals.Electrons held lesstightly.

Atomic SizeAtomic Size

Size goes UP on going down a group.

Because electrons are added further from the nucleus, there is less attraction.

Size goes DOWN on going across a period.

Size goes UP on going down a group.

Because electrons are added further from the nucleus, there is less attraction.

Size goes DOWN on going across a period.

SIZE

Atomic Radii

Trends in Atomic Size

0

50

100

150

200

250

0 5 10 15 20 25 30 35 40

Li

Na

K

Kr

He

NeAr

2nd period

3rd period 1st transitionseries

Radius (pm)

Atomic Number

0

50

100

150

200

250

0 5 10 15 20 25 30 35 40

Li

Na

K

Kr

He

NeAr

2nd period

3rd period 1st transitionseries

Radius (pm)

Atomic Number

Sizes of Transition ElementsSizes of Transition Elements

3d subshell is inside the 4s subshell.

4s electrons feel a more or less constant Z*.

Sizes stay about the same and chemistries are similar!

Ion SizesIon Sizes

F,64 pm9e and 9p

F- , 136 pm10 e and 9 p

-Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?

Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?

Ion SizesIon Sizes

ANIONS are LARGER than the atoms from which they come.

The electron/proton attraction has gone DOWN and so size INCREASES.

Forming Forming an anion.an anion.Forming Forming an anion.an anion.F,64 pm

9e and 9pF- , 136 pm10 e and 9 p

-

Ion SizesIon Sizes

Li,152 pm3e and 3p

Li+, 60 pm2e and 3 p

+Does the size goDoes the size goup or down up or down when losing an when losing an electron to form electron to form a cation?a cation?

Does the size goDoes the size goup or down up or down when losing an when losing an electron to form electron to form a cation?a cation?

Ion SizesIon Sizes

. CATIONS are SMALLER than the atoms from which they come.

The electron/proton attraction has gone UP and so size DECREASES.

Li,152 pm3e and 3p

Li+, 60 pm2e and 3 p

+Forming Forming a cation.a cation.Forming Forming a cation.a cation.

Trends in Ion Sizes

Redox Reactions

Redox Reactions

Why do metals lose electrons

in their reactions?

Why does Mg form Mg2+

ions and not Mg3+?

Why do nonmetals take on

electrons?

Why do metals lose electrons

in their reactions?

Why does Mg form Mg2+

ions and not Mg3+?

Why do nonmetals take on

electrons?

Ionization EnergyIonization Energy

IE = energy required to remove an electron from an atom in the gas phase.

Mg (g) + 738 kJ ---> Mg+ (g) + e-

Mg+ (g) + 1451 kJ ---> Mg2+ (g) + e-

Trends in Ionization Energy

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 350

500

1000

1500

2000

2500

1st Ionization energy (kJ/mol)

Atomic NumberH Li Na K

HeNe

ArKr

Trends in Ionization EnergyTrends in Ionization Energy

IE increases across a period because Z* increases.

Metals lose electrons more easily than nonmetals.

Metals are good reducing agents.

Nonmetals lose electrons with difficulty.

Trends in Ionization EnergyTrends in Ionization Energy

IE decreases down a group

Because size increases.

Reducing ability generally increases down the periodic table.

Electron AffinityA few elements GAIN electrons to

form anions.

Electron affinity is the energy involved when an anion loses an electron.

A-(g) ---> A(g) + e- E.A. = E

Affinity for electron increases across a period (EA becomes more positive).

Affinity decreases down a group (EA becomes less positive).

Atom EAAtom EAFF +328 kJ+328 kJClCl +349 kJ+349 kJBrBr +325 kJ+325 kJII +295 kJ+295 kJ

Atom EAAtom EAFF +328 kJ+328 kJClCl +349 kJ+349 kJBrBr +325 kJ+325 kJII +295 kJ+295 kJ

Trends in Electron Affinity

Trends in Electron Affinity

1 2 3 4 5 6 7S1

S2

S3

S4

0

50

100

150

200

250

300

350

Ele

ctro

n a

ffinit

y (

kJ/m

ol)

Group

Period

1 2 3 4 5 6 7S1

S2

S3

S4

0

50

100

150

200

250

300

350

Ele

ctro

n a

ffinit

y (

kJ/m

ol)

Group

Period

HH

FF ClClBrBr

CCSiSi

OOSS

SeSe

PPGeGe

KK

02_29

1H

3Li

11Na

19K

37Rb

55Cs

87Fr

4Be

12Mg

20Ca

38Sr

56Ba

88Ra

21Sc

39Y

57La*

89Ac†

22Ti

40Zr

72Hf

104Unq

23V

41Nb

73Ta

105Unp

24Cr

42Mo

74W

106Unh

25Mn

43Tc

75Re

107Uns

26Fe

44Ru

76Os

108Uno

27Co

45Rh

77Ir

109Une

110Uun

111Uuu

28Ni

46Pd

78Pt

29Cu

47Ag

79Au

30Zn

3 4 5 6 7 8 9 10 11 12

48Cd

80Hg

31Ga

49In

81Tl

5B

13Al

32Ge

50Sn

82Pb

6C

14Si

33As

51Sb

83Bi

7N

15P

34Se

52Te

84Po

8O

16S

9F

17Cl

35Br

53I

85At

10Ne

18Ar

36Kr

54Xe

86Rn

2He

58Ce

90Th

59Pr

91Pa

60Nd

92U

61Pm

93Np

62Sm

94Pu

63Eu

95Am

64Gd

96Cm

65Tb

97Bk

66Dy

98Cf

67Ho

99Es

68Er

100Fm

69Tm

101Md

70Yb

102No

71Lu

103Lr

1A

2A

Transition metals

3A 4A 5A 6A 7A

8A1

2 13 14 15 16 17

18

Alk

ali

me

tals

Alkalineearth metals Halogens

Noblegases

*Lanthanides

 † Actinides

Increasing Periodic Trends

electronegativity, ionization energy, ionic radii, electron affinity

atomic radii

ionic & atomic radii

ionization energy,electron affinity, & electronegativity

02_29

1H

3Li

11Na

19K

37Rb

55Cs

87Fr

4Be

12Mg

20Ca

38Sr

56Ba

88Ra

21Sc

39Y

57La*

89Ac†

22Ti

40Zr

72Hf

104Unq

23V

41Nb

73Ta

105Unp

24Cr

42Mo

74W

106Unh

25Mn

43Tc

75Re

107Uns

26Fe

44Ru

76Os

108Uno

27Co

45Rh

77Ir

109Une

110Uun

111Uuu

28Ni

46Pd

78Pt

29Cu

47Ag

79Au

30Zn

3 4 5 6 7 8 9 10 11 12

48Cd

80Hg

31Ga

49In

81Tl

5B

13Al

32Ge

50Sn

82Pb

6C

14Si

33As

51Sb

83Bi

7N

15P

34Se

52Te

84Po

8O

16S

9F

17Cl

35Br

53I

85At

10Ne

18Ar

36Kr

54Xe

86Rn

2He

58Ce

90Th

59Pr

91Pa

60Nd

92U

61Pm

93Np

62Sm

94Pu

63Eu

95Am

64Gd

96Cm

65Tb

97Bk

66Dy

98Cf

67Ho

99Es

68Er

100Fm

69Tm

101Md

70Yb

102No

71Lu

103Lr

1A

2A

Transition metals

3A 4A 5A 6A 7A

8A1

2 13 14 15 16 17

18

Alk

ali

me

tals

Alkalineearth metals Halogens

Noblegases

*Lanthanides

 † Actinides

Periodic Table of the Elements