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Chapter 2•Atoms,
Molecules, & Ions
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Atomic Theory• Elements composed of atoms
• Atoms can’t be changed
• Compounds of multiple atoms
• John Dalton
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Conservation of Mass
•In ordinary chemical reactions, matter can be neither created nor
destroyed
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Constant Composition
•Compounds contain elements that are always in the same proportions
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Multiple Proportions
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•The elements making up a compound will form whole number ratios
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Atom•The smallest particle that an element can be broken down into and still maintain the properties of the element
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Nuclear Atom•Proved by
Rutherford & Bohr in the famous gold foil experiments
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Atomic Composition
•Proton: in the nucleus
•Neutron: in the nucleus
•Electron: outside the nucleus
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Proton•In Nucleus
•+1 charge
•About 1 amu in mass
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Neutron•In nucleus
•Neutral in charge
•Mass is about 1 amu
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Electron•Outside the nucleus•-1 in charge•Negligible mass about 1/2000 amu
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Electron Charge•Determined by
Robert Milliken in the famous oil
droplet experiment
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Drill: Convert: 1) 23 cm/ms to km/ns 2) 56 g/nL to kg/ML
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Atomic Number•The number of protons in an element
•Z number
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Mass Number•The number of protons and neutrons in an atom
•A - number
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Nuclear Symbol• A 4
• X He• Z 2
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Isotopes•Atoms that contain the same number of protons, but different number of neutrons
•Z constant, A variable
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Atomic Mass• The weighted average mass of
all the isotopes of an element• average of relative abundance
x mass number for each isotope
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Periodic Table•Graphic representation of all the elements indicating size, charge, electronic structure, & reactivity
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Periods•Rows which indicate
energy level or shell or size of the atoms
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Groups or Families
•Columns which indicate the number of electrons in the outermost energy level determining charge & reactivity
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Metals•Left three quarters of the chart
•Lose electrons
•Become positive
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Nonmetals•Upper right portion•Gain, lose, or share electrons when they react
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Metalloids•Along the stair-stepped line from B to At
•Share properties of metals & nonmetals
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Radioactivity•The spontaneous breakdown of an unstable nucleus
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Radioactive Decay
•Alpha radiation
•Beta radiation
•Gamma radiation
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Alpha Particle•Helium nucleus•2 protons & two neutrons•mass = 4 & charge = +2•Low penetrating power
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Beta Particle•High speed electron
•Mass = 0 & charge = -1
•Medium penetrating power
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Gamma Rays•High energy electromagnetic wave
•No mass or charge
•Very high penetrating power
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Drill:•List & describe each of the three
radioactive particles
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Compound•A group of atoms that are chemically
combined
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Molecule•A compound that can exist by itself
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Diatomic Molecule
•Two atoms of the same element that are
chemically combined
•Cl2, F2, O2
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Ion•Charged Particle
•Cl-1
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Polyatomic Ion•A group of atoms chemically combined that together has a charge
•SO4-2
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Binary Compound•A compound made up of two elements in any ratio
•NaCl
•Mg3P2
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Chemical Formula•A formula that shows the number and kinds of atoms in a compound
•CaCO3
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Molecular Formula•A formula that shows the number and kinds of atoms in a molecule
•C6H12O6
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Atomic Structure•List & describe the
three subatomic particles
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Atomic Structure•Fill in the Chart:
• Isotope protons neutrons electrons
• U-235 - - -
• - 56 80 -
• - - 14 13
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Calculate the atomic mass of the element made up of the
following isotopes:99.50 % H-10.30 % H-20.20 % H-3
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Calculate the atomic mass of the element made up of the
following isotopes:5.0 % Pu-242, 5.0 % Pu-243
80.0 % Pu-244, & 10.0 % Pu-245
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Determine the number of of atoms in each
compound
•C6H12O6 NaNO3
•H3PO4 Al2(SO4)3
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List & describe each of the three types of radiation
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Chapter 2 General
•Define all the Key Terms on page 48
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Nuclear Symbols
•Work problems:
11 - 18
on page 50
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Nuclear Symbols
•Work problems:
19 - 24
on page 50
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Elements & PT
•Work problems:
27 - 88
on page 51
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Nomenclature
•Work problems:
45 - 48
on page 51
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Nomenclature
•Work problems:
49 - 54
on page 51
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Nomenclature
•Work problems:
55 & 56
on page 52