Download Fall.2008.Week5.Lesson.1 - reich

Chemistry SM-1131
Week 5 Lesson 1
Dr. Jesse Reich
Assistant Professor of Chemistry
Massachusetts Maritime Academy
Fall 2008
Class Today
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Test Wednesday
Poem
Movie
Review: Periodic Table, Isotopes and Atomic Mass
Atomic Mass
Review for the test
Quote
• Everything has to change, and that change has
to start with me. -Utah Phillips
Just be careful because change will hurt.
-D. Reich
Oil drop Movie
• http://chemistry.umeche.maine.edu/~amar/fa
ll2004/Millikan.html
Skipping Ahead
• I’m skipping a lot of scientists and a lot of
story
• We have a nucleus and it contains Protons and
Neutrons
• Electrons are on the outside in set patterns
Nucleus Masses
• Protons have masses of 1.67262e-27kg
• Neutrons have masses of 1.67493e-27kg
• OK, talking about that mass is obnoxious. So
chemists came up with another scheme. They
took an atom of Carbon, which has 6 neutrons
and 6 protons, and they said 1/12 of that mass
is now 1 amu.
• Protons by themselves have a mass of 1.0073
amu. Neutrons have a mass of 1.0087 amu.
Electrons
• Protons are over 1800 times larger than
electrons. So, chemists say electrons have no
mass.
• This is not exactly true, it’s more like they have
negligible mass.
Charge
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Protons have a charge of +1
Electrons have a charge of -1
Neutrons have no charge at all.
Oppositely charged particles attract.
Similarly charged particles repel.
If an atom has an equal number of protons
and electrons the atom has no charge. For
every extra proton it has +1 charge. For every
extra electron it has -1 charge.
Periodic Table
Hydrogen is the element
1 is the atomic number
1.0079 is the atomic mass
Elements
• The number of protons is called the atomic
number.
• If two elements have the same atomic number
they are the same element. If two elements
have different atomic numbers they are
different.
The Table
Groups/families are up and down
Rows/periods are left to right
The Table
Group 1. Alkali Metals
Group 2. Alkaline Earth Metals
Group 3-12 Transition Metals
Group 17. Halogens
Group 18. Noble Gases
Main group 1,2 13-18
H, C, N, O, P, S, Se are organic elements
57-71 lanthanides
89-103 actinides
B, Si, Ge, As, Sb, Te, Po are metaloids
Metals
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Shiny
Reflect
Malleable (bendable)
Ductile (can be drawn into strips)
Conduct electricity
LOSE ELECTRONS
Non-Metals
• Dull
• Brittle
• Don’t conduct
• GAIN ELECTRONS
(think graphite)
Metalloids
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Mixed Properties
Semiconductors
Some dull, some shiny
Etc.
Ions
• Any charged particle is called an ion.
• # of Protons - # of Electrons = charge
• If # of protons = # of electrons the charge is 0
and we call it neutral (not an ion)
• If # of protons > # of electrons it has a positive
charge and we call it a cation.
• If # of protons < # of electrons it has a positive
charge and we call it an anion.
Isotopes
• If two elements are the same they will have
the same # of protons.
• If two atoms of the same element have
different numbers of neutrons they are called
Isotopes.
Ways to write Isotopes
• Two systems exist to write Isotopes.
• Let’s take Chlorine for Example. There are two
major isotopes of chlorine. One where the
atom has 17 protons and 18 neutrons and one
where it has 17 protons and 20 neutrons.
• The easy way to write it is Cl-35 or Cl-37.
• Or 3517Cl, and 3717Cl.
• Top number = Mass #
• Bottom = Atomic Number (# of protons)
Mass Number
• Simply put the mass is:
• # of protons + # of neutrons = atomic number
Atomic Mass
• Atomic Mass is actually pretty complex.
It’s an average mass of all the different isotopes.
(%abundance * mass) + (%abundance*mass)
etc… = atomic mass
Neon
• Neon is made up to 3 isotopes
• Ne-20 = 90.38%
• Ne-21 =0.27%
• Ne-22 = 9.25%
• Atomic mass =
20.00*.9038 + 21.00*.0027 + 22.00*.0925 =
20.1677 = 20.17 amu = atomic mass
So the masses on the periodic tables are average
masses of all the isotopes
Get Ready
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TEST WEDNESDAY!!!
1: scientific method, vocab words
2: sig fig, rounding, density
3: Matter and Energy, chemical vs. physical,
temperature, heat capacity
• 4: Atomic Theory, scientists, protons,
neutrons, electrons, periodic table, Ions,
Isotopes, Atomic Mass, Atomic Number