Law of Conservation of Mass

Law of Definite Proportions

Law of Multiple Proportions

Atom

Thomson’s Cathode-Ray Tube Experiment

Millikan’s Oil Drop Experiment

Rutherford’s Gold Foil Experiment

Periodic Table of the Elements

Atomic Number (Z)- the atomic number is unique for each element- provides the number of protons that an element has

6

CCarbon

12.0107

- IF the element is neutral, it also provides the number of electrons

Atomic #

Atomic symbol

Mass Number

- the mass number is the number of protons and neutrons in a particular element

6

CCarbon

12.0107

- To find the number of neutrons subtract the number of protons (atomic number) from the mass number.

Mass Number

- the atomic mass of the element in amu (atomic mass unit)

6

CCarbon

12.0107

26

FeIron55.845

36

KrKrypton

83.798

ExamplesFind the number of protons, electrons, and neutron in the following:

Protons:

Electrons:

Neutrons:

Ions- elements or group of elements that have gained or lost electrons.- if an element loses electrons it is a positive ion or cation.- if an element gains electrons it is a negative ion or an anion.

Examples:sodium (Na)p -e -n -

oxygen (O)p -e -n -

sodium ion (Na+) p -e -n -

oxygen ion (O2-)p -e -n -

Isotopes- atoms of the same element with different masses.- mass numbers will be different.- since mass #’s are different, the number of neutrons are not the same.

Some isotopes have unique names, some do not.H-1 (hydrogen) H-2 (deuterium) H-3 (tritium)

C-12 (carbon 12) C-13 (carbon 13) C-14 (carbon 14)

Examples:carbon-12 carbon-14 p - p - e - e -n - n -

Average Atomic Mass- weighted average of atomic masses of naturally occurring isotopes of an element.

Example: Copper

copper-63 – 62.929598 69.17% of all coppercopper-65 – 64.927793 30.83% of all copper

What is the weighted atomic mass of copper? 63.546 amu

Average Atomic Mass

Avogadro’s Number- the number of particles in exactly one mole of a pure substance.- 6.022 x 1023 particles (atoms or molecules)

The Mole (mol)- the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12.- the mole is a counting unit

Molar Mass- mass of one mole of a pure substance- numerically it is equal to the atomic mass of the element or compound.- the unit used is g/mol.- when using molar mass, use 4 significant figures!

The Mole

Avogadro’s Number

Molar Conversions- molar mass and Avogadro’s number can be used as conversion factors to convert from one unit to another

1 mol = 6.022 x 1023 atoms/molecules

1 mol = molar mass of = any element or compound

moles → gramsgrams → molesmoles → atomsatoms → molesatoms → gramsgrams → atoms

There are six conversions: