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