Download PPT Atoms and Periodicity

Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Review Unit 1 (Chp 6,7):
Atoms, Electrons,
& Periodicity
John D. Bookstaver
St. Charles Community College
St. Peters, MO
 2006, Prentice Hall, Inc.
Development of Atomic Models
1803 Dalton
Atomic Theory
1904 Thomson
Plum Pudding
1911 Rutherford
Nuclear Model
+
Isotopes
element: same or different
mass: same or different
why? same # of protons (& electrons),
but different # of neutrons
1
H
1
protium
2
H
1
deuterium
3
H
1
tritium
Average Atomic Mass
• average atomic mass: calculated as a
weighted average of isotopes by their
relative abundances.
• lithium-6 (6.015 amu), which has a
relative abundance of 7.50%, and
• lithium-7 (7.016 amu), which has a
relative abundance of 92.5%.
(6.015)(0.0750) + (7.016)(0.925) = 6.94 amu
Avg. Mass = (Mass1)(%) + (Mass2)(%) …
Mass Spectrometry
isotopes
separated
by
difference
in mass
Development of Atomic Models
1803 Dalton
Atomic Theory
1904 Thomson
Plum Pudding
1911 Rutherford
Nuclear Model
1913 Bohr
Shell Model
1926 Quantum Mechanical
Model
+
What
evidence
?
5.3
Atomic Emission Spectra
• elements give discrete lines of E & f.
(only specific colors of energy & frequency)
Bohr’s Shell Model
(1913–Niels Bohr)
electrons occupy only specific levels (or shells)
of “quantized” energy
(& wavelength & frequency)
Electrons as Waves
quantized into
specific multiples
of
wavelengths,
but none
in between.
Bohr’s Shell Model
EXCITED
state
e–’s absorb
(+) energy,
move to
outer
levels
(n=2 to n=5)
5
2
∆E
e–’s emit
(–) energy,
move back
to inner
levels
(n=5 to n=2)
GROUND
state
4
2
3
2
Which transition shows a light wave
of the greatest energy? n=5 to n=2
R
O
Y
G
B I V
Electromagnetic Spectrum
Lowest Energy
Highest Energy
(higher ) (shorter )
• All EM radiation travels at the speed of light (c),
2.998  108 m/s. c = 
E = h (of 1 photon)
Aufbau: Fill lowest energy
orbitals first.
1s2 2s2 2p6 3s2 3p6 4s2 3d104p2
Hund: 1 e– in equal orbitals before pairing
()
(3d fills after 4s)
?
Pauli Exclusion:
no e–’s same props
(opp. spin) (↑↓)
nucleus
+
• Paramagnetic:
species are attracted by a magnet
(caused by unpaired electrons).
Fe:
[Ar] ↑↓
↑↓ ↑ ↑ ↑ ↑
4s
3d
• Diamagnetic:
species are slightly repelled by magnets
(caused by all paired electrons)
Zn:
[Ar] ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
4s
3d
• d block metals lose their outer s electrons
before any core d electrons to form ions.
Fe
1s2 2s2 2p6 3s2 3p6 4s2 3d6
Fe2+ 1s2 2s2 2p6 3s2 3p6 3d6
Fe3+ 1s2 2s2 2p6 3s2 3p6 3d5
• d block (trans. metals) have colored ions
due to light excited e– movement in d orbitals
Other Aspects
List 3 species isoelectronic with Ca2+ & S2–.
P3– , Cl– , Ar, K+ , Sc3+ , Ti4+, V5+, Cr6+, Mn7+
Arrange the following species by increasing size:
Ar, K+, Ca2+, S2–, Cl–
Ca2+ < K+ < Ar < Cl– < S2–
Spectroscopy
SPECTROSCOPIC TECHNIQUE
Microwave
IR
EM REGION
Molecular Structure by
Microwave molecular Rotation
Infrared
Vis/UV Atomic Emission Spectra Visible &
(lines of frequencies/colors)
PES (Photoelectron Spectroscopy)
APPLICATION
Ultraviolet
X-ray
Types of bonds by
bond Vibration
Transition of e–’s
between energy levels
Ionization of e–’s
shows e– configuration
WATCH this 6 min Video Explanation of PES at HOME.
Relative # of e–’s
Photoelectron Spectroscopy (PES)
Which peak is H and which is He?
higher peak = more e–’s
1s2
He 1s1
H
6
5
4
3
2
1
0
Binding Energy ...or Ionization Energy
(MJ/mol)
(required to remove e–’s)
 further left = more energy required
(stronger attraction
due to more protons)
Relative # of e–’s
Photoelectron Spectroscopy (PES)
Which peak is H and which is He?
6
2p
–
Ne
?
higher peak = more e ’s
1s2
Identify the
1
He
1s
2
1s2
2s
element
H
& e-config
6
5
4
3
2
1
0
Binding Energy ...or Ionization Energy
(MJ/mol)
(required to remove e–’s)
 further left = more energy required
(stronger attraction
due to more protons)
PES (A)
Identify
element
(A)
Ge
WS
#1,5
Identify
element
(B)
K
3d10
2p6
1s2
n=1
2s2
n=2
3p6
3s2
n=3
4s2 4p2
n=4
PES (B)
4s1
?
Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Review Unit 1 (Chp 7):
Periodicity
…or…
Periodic Trends in
Atomic Properties
John D. Bookstaver
St. Charles Community College
St. Peters, MO
 2006, Prentice Hall, Inc.
Periodic Trends
• We will explain observed trends in
size
Atomic (and Ionic) Radius
lose e– Ionization energy
attract e– Electronegativity
Zeff & shielding
(explains all periodic trends and properties)
Zeff & Shielding
• effective nuclear charge, (Zeff): Zeff = Z − S
Z = nuclear charge (+proton’s)
S = shielding (core e–’s)
attraction
• shielding, (S):
shielding
inner core e–’s shield valence
Zeff
e–’s from nuclear attraction.
Z = +11
+11
Na atom
Zeff = +1
Atomic Radius
decreases across a period
-due to increasing Zeff
(more protons)
att.
=shield
Zeff
increases down a group
-due to
increasing
shielding
(more
energy
levels)
att.
shield
=Zeff
Ionic Radius
Why?
• Cations are
• Anions are
smaller than atoms.
larger than atoms.
loses a shell
core shell closer to
nucleus
new valence e– ‘s
less shielded
(greater Zeff)
electrons are
added and
repulsions are
increased
(same Zeff &
same shielding)
Ionization Energy (IE)
•
•
•
•
energy required to remove an electron
more energy to remove each electron
IE1 < IE2 < IE3, … look for a huge jump in IE
once all valence e–’s are removed, the next e– is on
an inner level with attraction (shielding & Zeff).
huge jump in IE4 b/c 4th e– on inner level
(must have 3 valence e–’s)
Trends in First IE
IE tends to…
increases across a period
decreases down a group
-due to increasing Zeff
(more protons)
att.
=shield
Zeff
-due to
increasing
shielding
(more
energy
levels)
att.
shield
=Zeff
Trends in Electronegativity (EN)
decreases down a group
-ability of an atom to attract electrons when
bonded with another atom.
increases across a period
-greater Zeff
-more
shielding
(more
energy
levels)
Periodic Trends (Summary)
Electronegativity
Can you explain all of this
in terms of p’s and e’s?
Electronegativity
Zeff & shielding
WS #2,3
Atomic radius