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

Chapter 2 General

•Define all the Key Terms on page 48

Nuclear Symbols

•Work problems:

11 - 18

on page 50

Nuclear Symbols

•Work problems:

19 - 24

on page 50

Elements & PT

•Work problems:

27 - 88

on page 51

Nomenclature

•Work problems:

45 - 48

on page 51

Nomenclature

•Work problems:

49 - 54

on page 51

Nomenclature

•Work problems:

55 & 56

on page 52