CHAPTER 2 – ATOMS AND
ELEMENTS
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Atoms (2.1)
Elements (2.2)
Atomic and mass number (2.3)
Periodic Table (2.4)
The Mole (2.5)
Radioisotopes (2.6, 2.7)
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CHEM 5 - ROBERTS
I. Atoms
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IA. Dalton's definition
IB. Subatomic particles
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1. Discovered by land mark experiments
2. Particles
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a. electron (charge and mass)
b. proton (charge and mass)
c. neutron (charge and mass)
IC. Atomic models
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1. Rutherford's discovery
2. Shell model
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IB. Subatomic Particles
TABLE 2-1
Subatomic Particle
Subatomic Particles
Mass (amu)
Charge
Proton
1.00728
1+
Location in Atom
Nucleus
Neutron
1.00867
0
Nucleus
Electron
0.00055
1-
Outside of
1 amu ~ 10-24 g!
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II. Elements
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IIA. Definition and examples
IIB. Atomic names and symbols
IIC. Elements in the body
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1. Bulk vs trace elements
2. Elements in the diet (Healthlink)
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a. Example - iron deficiency and overload (hemochromatosis)
IID. Atomic and mass number
1. Atomic number
2. Mass number
3. Using mass and atomic numbers to find neutrons
IIE. Isotopes
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IIA. Elements - examples
Two forms of the element carbon
Bromine and copper
Fig. 2.2
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Fig. 2.3
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IIB. Atomic names and symbols
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IIC. Elements in the body
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IIC. Elements and dietary needs
Iron deficiencies
Iron overload
Hemochromatosis
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IID. Atomic and mass numbers
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Give the atomic and mass numbers of
an element containing eight protons and
ten neutrons
How many neutrons and protons in the
element shown?
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IIE. Isotopes
• Atoms with same number of protons but different number of neutrons
• Some isotopes are radioactive
Fig. 2.5
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Practice – Mass #, atomic #,
isotopes
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What element has...
• 36 protons? 16 protons? 53 protons? 20
protons?
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Find the # of p, n, e in 24Mg, 55Mn, 64Zn,
74Se
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III. The Periodic Table
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IIIA. Importance
IIIB. Symbols and numbers
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IIIC. Organization
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1. Atomic number
2. Atomic mass (weight)
1. Groups and periods
2. Classification of elements (broad)
3. Classification of elements (group A elements)
IIID. Atomic Mass
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1. Definition
2. Atomic masses in the periodic table reflect isotopes
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III. The Periodic Table
Groups
Periods
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IIID. Atomic Mass
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Atomic mass = atomic weight, measured
in amu
1 amu = 1.661 x 10-24 g
Atomic mass is not the same as mass
number!
Atomic masses in the periodic table are
averages of the isotopes
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Practice – Atomic weight
calculations
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The atomic wt of Br is 79.9 amu. Br has
two isotopes, Br-79 and Br-81. What are
their approximate relative proportions?
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What would be the atomic weight of a
30:70 mix of Br-79 and Br-81?
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IV. The Mole
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IVA. Atomic dimensions
IVB. The mole
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1. Counting unit
2. Definition of mole
3. Scale of mole
4. Atom-mole conversions
IVC. Molar mass
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1. Definition
2. Relationship to atomic mass
3. Gram-mol conversions
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IVA. Atomic dimensions
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Diameter ~ 10-10 meters
• Human hair = 100,000 nanometers
• Red blood cell = 10,000 nanometers
• Typical atom = 10 nanometers
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Mass ~ 10-23 g
• Ant = 0.005 g
• Atom = 0.00000000000000000000001 g
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IVB. The Mole – Avogadro’s
number
1 mol = 6.022 x 1023
Hg
C
Co
Zn
Fig. 2.9
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Fig. 2.8
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Atom-mol conversions
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Two conversion factors you can use
Examples
• How many C atoms are in 0.023 mol?
• How many mol is 10,000 K atoms?
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IVC. Molar Mass
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The weight of 1 mol of atoms
Numerically equivalent to amu
• 1 C atom = 12 amu
• 1 mol C atoms = 12 g
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Allows conversion between mass and
number of particles
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Practice - g-mol conversions
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How many g of C are in 0.5 mol?
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How many atoms of Pb are in 12.1 g?
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V. Radioisotopes
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VA. Definition
VB. Types
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1. alpha particles
2. beta particles
3. positrons
4. gamma rays
VC. Half-life
VD. Radioisotopes in medicine
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V. Radioisotopes
TABLE 2-4
Common Forms of Radioactivity
Velocity1
Penetrating Ability
2+
5–10% of light speed
Low
Electron
1-
Up to 90% of light speed
Moderate
Positively charged electron
1+
Up to 90% of light speed
Moderate
Electromagnetic radiation
0
Light speed
High
Name
Symbol
Alpha
α
Makeup
2 protons + 2 neutrons
Charge
Beta
β
Positron
β+
Gamma
γ
Shielding
Fig. 2.13
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VC. Half-life, t1/2
Fig. 2.14
After 1 half-life, 50% decay
After 2 half-lives, 75% decay
After 3 half-lives, ???
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VC. Half-life - example
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32 g of 32P are generated. How much
will be left after three half-lives? The t1/2
of 32P is 14 days.
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2 biggest uses:
Cancer treatment
Diagnostics (detection)
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VD. Radioisotopes – Diagnosis
and therapy
Radiation damages cells
by destroying DNA
Before
After
Thyroid scan after 131I treatment
Fig. 2.15
Fig. 2.11
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Example: Positron Emission
Tomography
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Uses of
t1/2 = 110 minutes
Attached to
glucose
Brain utilizes
glucose
Scan for
Alzheimer’s
Source: www.alzheimers.org
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Example: treating brain tumors
Boron Neutron Capture Therapy (experimental)
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Boron-10 concentrates
in brain tumors
Patient is treated with
thermal neutrons,
absorbed by the boron
Creates α-particles,
killing the cancer cells
Patient is treated at a
nuclear reactor
http://en.wikipedia.org/wiki/File:BNCT-kaaviokuva.png
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