Chemistry Honors Unit 3

The law of constant composition

states that a chemical compound always contains its component elements in fixed ratio by mass, regardless of the source or amount of the compound.

The law of conservation of mass

states that mass is neither created nor destroyed in a chemical reaction; the mass of the products equals the mass of the reactants.

The law of multiple proportions

states that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers.

alpha

positively charged, +2, stopped by paper fast-moving electrically charged particles

beta

negatively charged, -1, stopped by aluminum fast-moving electrically charged particles

gamma

no charge

Rutherford’s Gold Foil Experiment

Atom are mostly empty space

existence of dense positively charged nucleus

Millikan’s Oil Experiment

measure charge of an electron

The mass of an electron

Rutherford’s Radiation Experiment

Radioactivity consists of three distinct types of radiation (differ in their response to an electric field)

Alpha-High Speed Electron

beta-Helium Nucleus

gamma-x-rays

JJ Thomson’s Cathode Ray Tube

Cathode Ray is negatively charged

discovered electrons

subatomic particle

proved atom weren’t indivisible

Isotopes

atoms of elements with different #’s of neutrons

different masses but all have the same # of protons

Group (1-8)

number of valence or bonding electrons for all elements in a group

Covalent Bonds

Sharing of electrons, forms molecules by combining 2 or more NONMETALS to achieve full outer shells.

Ionic Bonds

transfer of electrons forms “formula units” by combining a metal and a nonmetal or a group of nonmetals resulting in charged ions that attract each other.

polyatomic ion

a group of nonmetals

cation

a positively charged ion formed when an atom loses one or more electrons.

anions

negatively charged ions formed when an atom gains one or more electrons.

ions

forms when neutral atoms lose or gain electrons

octet rule

“Eight is the magic number” when a bond is formed between a metal and nonmetal

Ions

are charged particles that form when atoms lose or gain electrons, resulting in either positive cations or negative anions.

Ionic compound

is a chemical compound composed of ions held together by ionic bonds, usually formed between metals and nonmetals.

Properties of a Nonmetal

dull, brittle solids (or gases/liquids), poor conductors of heat/electricity, and have lower melting points.

Properties of a Metal

are shiny, malleable, ductile solids, good conductors of heat/electricity, and have higher melting points.

Proporties of a Metalloids

are intermediate in properties between metals and nonmetals, often showing characteristics of both, and can be semiconductors.