modern atomic theory chapter 10. ancient greeks’ view of matter about 400 b.c., aristotle thought...
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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.
Electromagnetic Radiation
Radiant energy that exhibits wave-like behavior and travels through space at the speed of light in a vacuum.
The electromagnetic spectrum.
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.
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
24 17
63
58X
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.
AluminumAluminumGroup 3A
Atomic number = 13
1s2 2s2 2p6 3s2 3p1
[Ne] 3s2 3p1
1s
2s
3s3p
2p.
:Al
PhosphorusPhosphorusGroup 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
: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 transition elements have the configuration (n-1) d. D orbitals are always one behind their period.
CopperIronChromium
Transition Element Configurations
3d orbitals used for Sc - Zn
3d orbitals used for Sc - Zn
Lanthanides and ActinidesLanthanides and Actinides
Rare earth elements always have the configuration (n-2) f. F orbitals are always two behind their period.
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
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, the addition of protons pulls electrons tighter.
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, the addition of protons pulls electrons tighter.
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
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
. 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
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
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
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