Download Unit 2 Notes - School City of Hobart

AP CHEMISTRY
UNIT 2 – Atoms, Molecules, and Ions
Learning Goals:
1. Students will understand the general history of chemistry
including scientific theories, laws, and evidence.
2. Students will be able to apply concepts/rules of chemical
nomenclature to name compounds and correctly write formulas.
3. Students will understand why substances are radioactive, how
those samples decay, and be able to illustrate different equations
representing those nuclear reactions.
Chapter 2 – Atoms, Molecules, and Ions
Check out the following web address if you want a quick run-down on the atomic
theory … http://en.wikipedia.org/wiki/Atomic_theory
2.1 The Atomic Theory of Matter
• Ancient Greece → Democritus described the material world as being
made up of tiny indivisible particles called atomos
• Fast forward to 17th Century Europe → John Dalton comes up with
the 1st Atomic Theory
1.
2.
3.
4.
2.2 The Discovery of Atomic Structure
• How do we know about subatomic particles? (atoms)
- J.J. Thompson discovered negative particles using cathode rays
**Led to the Plum-pudding model of an atom (p.43)
- Robert Millikan discovered an electron’s charge in his oil-drop experiment
- Henri Becquerel discovered radioactive particles (nuclear chemistry)
- Ernest Rutherford discovered the nucleus of an atom using radioactive
material with his Gold-foil experiment (p.44)
2.3 The Modern View of Atomic Structure
• Atoms are composed of 3 subatomic particles:
protons, neutrons, electrons
• A few basics on representing isotopes (atoms of the same element
with different masses) of elements …
Sample 2.3, p.47
2.5 The Periodic Table
• The periodic table is the most significant tool that chemists use for
organizing and remembering chemical facts
• Some key terms:
- Group
- Period
- Metal/Nonmetal/Metalloid
**2.6 → 2.8 discuss basic nomenclature … do we to review this again??
2.9 Some Simple Organic Compounds
The study of compounds of carbon is called organic chemistry
• Hydrocarbons are compounds that contain only carbon and hydrogen
• The simplest class of hydrocarbons is called the alkanes
- each carbon atom in an alkane is bonded to four other atoms
• Other classes of organic compounds are obtained when one or more
hydrogen atoms in an alkane is replaced with functional groups
- functional groups are specific groups of atoms
- An alcohol is a functional group where an H atom in an alkane
is replaced by an –OH group
Chapter 21 – Nuclear Chemistry
Nuclear reactions involve changes in atomic nuclei to generate energy.
Nuclear Chemistry is the study of those reactions, with an emphasis on their
uses in chemistry and their effects on biological systems
21.1 Radioactivity
• Nucleon is simply another name for particles in the nucleus (proton/neutron)
• Different isotopes of an element are distinguished by mass #’s
(Example: uranium-235 or 235U)
• A nuclide is a nucleus containing a specific # of protons and neutrons
• For a nuclide to be considered radioactive, it must have an unstable
nucleus due to an imbalance between # of protons and neutrons
~1:1 ratio = stable
*The further an isotope is from a 1:1 ratio, the more likely it is to be
radioactive (Figure 21.2, p.881)
• Types of Nuclear Decay (aka Radioactivity)
21.4 Rates of Radioactive Decay
• Ultimately, radioactive materials are unstable and decay until they
become something that is stable (lower proton:neutron ratio)
• Decay can occur through either alpha or beta emission
• How long does it take?
- depends on the isotope
- half-lives are different for different isotopes
- A half-life is the amount of time required for half of any given
quantity of a substance to react
Sample 21.6, p.887
The half-life of cobalt-60 is 5.3 yr. How much of a 1.000 mg sample
of cobalt-60 is left after 15.9 yr?
Sample 21.7, p.889
A rock contains 0.257 mg of lead-206 for every mg of uranium-238.
The half-life of uranium-238 to lead-206 is 4.5 x 109 yr. How old is
the rock?
Nuclear fission vs. Nuclear fusion