Atomic Theory, Periodic Table, and Chemical Properties

Dalton's 1st Postulate: Each element is composed of extremely small particles called atoms

TRUE

Dalton's 2nd Postulate: All atoms of a given element are identical in mass and other properties

FALSE

Dalton's 3rd Postulate: Atoms of an element are not changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed

TRUE

Dalton's 4th Postulate: Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kinds of atoms

TRUE

Law of Conservation of Mass

Total mass after a chemical process equals total mass before the process

J. J. Thomson

Used the cathode-ray experiment; discovered the electron and determined its charge-to-mass ratio

Thomson's Cathode-Ray Experiment

Cathode rays were deflected by electric and magnetic fields, showing they were negatively charged particles

Thomson's Atomic Model

Plum-pudding model: a positive sphere with negative electrons embedded throughout it

Robert Millikan

Used the oil-drop experiment to determine the charge of the electron

Millikan's Oil-Drop Experiment

Used electrically charged plates and charged oil drops to determine the electron's charge

Henri Becquerel

First observed radioactivity

Marie and Pierre Curie

Studied radioactivity

Radioactivity

Spontaneous emission of radiation by an atom

Ernest Rutherford

Used the gold-foil experiment; concluded that atoms have a tiny, dense nucleus and are mostly empty space; later discovered the proton

Rutherford's Gold-Foil Experiment

Fired alpha particles at thin gold foil; most passed through while a few were strongly deflected, showing that atoms are mostly empty space with a tiny, dense nucleus

James Chadwick

Discovered the neutron

Periodic Table Arrangement

Increasing atomic number

Rows on the Periodic Table

Periods

Columns on the Periodic Table

Groups

Elements in the Same Group

Have similar chemical properties

Periodicity

Repeating patterns of chemical properties and reactivities

Group 1A

Alkali metals

Group 2A

Alkaline earth metals

Group 6A

Chalcogens

Group 7A

Halogens

Group 8A

Noble gases / rare gases

A Groups

Main-group elements

Metals

Left side of the periodic table

Nonmetals

Right side of the periodic table, except hydrogen

Metalloids

Border the stair-step line

Physical Property

Can be observed without changing a substance into another substance

Chemical Property

Can only be observed when a substance changes into another substance

Boiling Point

Physical property

Density

Physical property

Mass

Physical property

Volume

Physical property

Flammability

Chemical property

Corrosiveness

Chemical property

Reactivity with Acid

Chemical property

Intensive Property

Does not depend on the amount of substance present

Extensive Property

Depends on the amount of substance present

Density

Intensive property

Boiling Point

Intensive property

Color

Intensive property

Mass

Extensive property

Volume

Extensive property

Energy

Extensive property

Physical Change

Does not change the composition of the substance

Chemical Change

Produces one or more new substances

Melting

Physical change

Boiling

Physical change

Freezing

Physical change

Change of State

Physical change

Change in Temperature

Physical change

Change in Volume

Physical change

Combustion

Chemical change

Oxidation

Chemical change

Decomposition

Chemical change

Filtration

Separates solid substances from liquids and solutions

Distillation

Separates a homogeneous mixture using differences in boiling points

Chromatography

Separates substances based on differences in solubility in a solvent

Significant Figures

Digits that were measured

Nonzero Digits

Significant

Zeros Between Significant Digits

Significant

Zeros at the Beginning of a Number

Not significant

Zeros at the End of a Number With a Decimal Point

Significant

Addition/Subtraction Sig-Fig Rule

Round to the least significant decimal place

Multiplication/Division Sig-Fig Rule

Round to the fewest significant figures

Accuracy

How close a measurement is to the true value

Precision

How close several measurements are to each other