III. Atomic Structure A. Components of atoms + - a) electron, e - (negatively charged), -1.6 x 10...
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Transcript of III. Atomic Structure A. Components of atoms + - a) electron, e - (negatively charged), -1.6 x 10...
III. Atomic Structure A. Components of atoms
+
-
a) electron, e- (negatively charged), -1.6 x 10-19 C mass = 1/1838 that of a H atom
Chapter 3
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b) proton, p+ (positively charged) mass mass of H atom
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Charge and Mass Characteristics of Electrons, Protons, and Neutrons.
c) Neutron, n (no charged) mass mass of H atom
unit charge
electron, e- (negatively charged), -1.6 x 10-19 C
3
atomic number, Z = number of protons in an atom of a given element
mass number, A = # of protons + # of neutrons = (# of nucleons)
d) Symbols of elements
XAZ
Examples
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B. Isotopes Not all atoms of the same element have the same mass
Example: There are 3 kinds of Hydrogen atoms H D T
hydrogen-1 hydrogen-2 hydrogen-3 (protium) (deuterium) (Tritium)
mass ratio 1 2 3
Symbol H H H
1 e-, 1 p+ 1 e-, 1 p+,1 n
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21
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Isotopes: Atoms with the same # of p+s and e-s but different # of n's. They have the same chemical properties except that they are different in mass 5
Examples
Isotopes are atoms of the same element with different number of neutrons.
C C12 6
14 6
All atoms of an element have the same atomic #
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C. Atomic mass (weight) – mass of an atom
Atomic mass unit (amu)
Mass of a H atom = 1.677 x 10-24 g
H11
1 amu
He42 4 amu
Li73 (3p+s,4 ns)
C (6 p+s, 6 ns)12 6
1 amu = 1.667 x 10-24 g
In the periodic table, not all atomic masses (atomic weights) are close to a whole number because of the existence of isotopes.
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Figure 3.3 The periodic table of the elements
Group
peri
od
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Example: Cl
35Cl 37Cl75% 25%
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Alk
ali m
etal
s
Alk
alin
e ea
rth
met
als
Hal
ogen
s
Nob
le g
ases
10
(Main group elements)
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Selected Physical Properties of Metals and Nonmetals.
NonmetalsNonmetals• Except for hydrogen (H), they lie on the right side of the Periodic Table.• Except for graphite, do not conduct electricity.• In chemical reactions, they tend to accept electrons.
MetalsMetals • are solids at room temperature (except for Hg, which is a liquid), shiny, conduct electricity, and are ductile and malleable.
• form alloys (solutions of one metal dissolved in another); brass, for example, is an alloy of copper and zinc
• In chemical reactions, they tend to give up electrons.
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MetalloidsMetalloids
• They have some of the properties of metals and some of nonmetals; for example, they are shiny like metals but do not conduct electricity.
• Six elements are classified as metalloids: boron, silicon, germanium, arsenic, antimony, and tellurium.
• One of the metalloids, silicon, is a semiconductor; it does not conduct electricity under certain applied voltages, but becomes a conductor at higher applied voltages.
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Tc
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D. The inner structure of the atom
Rutherford’s experiment
Observations1. Most of them ( particles) went right through
2. A few deflected3. Some bounced back from the gold foil
He2+
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http://video.google.com/videoplay?docid=-1909836802101196671&q=rutherford+experiment&total=8&start=0&num=10&so=0&type=search&plindex=0
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IV. Electron configuration of atoms
A. Experimental facts (Flame test)
A pure substance absorbs only certain energies andemit certain energies.
From quantum mechanical calculations, electrons canbe in discrete energy levels only
Bohr
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IV. Electron configuration of atoms
A. Experimental facts
A pure substance absorbs only certain energies andemit certain energies.
From quantum mechanical calculations, electrons canbe in discrete energy levels only
Bohr
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B. Energy levels
2 818
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Energy levels
a) Shells and subshells
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b) Orbitals Further studies indicate that electrons do not travel in circles
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Standing wave
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p orbitals
z
24
d orbitals
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Figure3.10
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c) Electron Spin
An electron in an orbital can either spin up or spin down
spin up
Spin down
N
S N
S
A spinning electrongenerates a tiny magnetic field
When their tiny magneticfields are aligned N-S, theelectron spins are paired
1
2
electron pair27
Electron Configuration and Orbital Diagrams
1s
2s
2p
3s
3p
H 1s 1
Orbital (box) diagram Electron configuration
He 1s 2
Pauli exclusive principle
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Electron Configuration and Orbital Diagrams
1s
2s
2p
3s
3p
Orbital diagram Electron configuration
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1s
2s
2p
3s
3p
Orbital diagram Electron configuration
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Copyright © Houghton Mifflin Company. All rights reserved. 3–13
Figure 3.11 The order of filling of various electronsubshells is shown on the right-hand side of this diagram. Above the 3p subshell,subshells of different shells "overlap".
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1s
2s
2p
3s
3p
Orbital (box) diagram Electron configuration
4s
3d
4p
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1s
2s
2p
3s
3p
4s
3d
4p
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Copyright © Houghton Mifflin Company. All rights reserved. 3–14
Figure 3.12 The order for filling electronsubshells with electrons follows the order given by the arrows in this diagram. Start with the arrow at the top of the diagram and work toward the bottom of the diagram, moving from the bottom of one arrow to the top o the next-lower arrow.
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1s
2s
2p
3s
3p
Orbital diagram Electron configuration
4s
3d
4p
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Copyright © Houghton Mifflin Company. All rights reserved. 3–15
Figure 3.13 Electron configurations and the positions of elements in the periodic table.
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Copyright © Houghton Mifflin Company. All rights reserved. 3–15
Figure 3.13 Electron configurations and the positions of elements in the periodic table.
3d
4d5d6d
4s
5s6s
7s
2s
3s
2p
3p
5p6p
4f
5f
4p
37
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Copyright © Houghton Mifflin Company. All rights reserved. 3–15
Figure 3.13 Electron configurations and the positions of elements in the periodic table.
3d
4d5d6d
4s
5s6s
7s
2s
3s
2p
3p
5p6p
4f
5f
4p
Os 1s22s22p6…………… 5d6
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