AP Chemistry - Unit 1

Pure Substance

Matter with a fixed composition; includes elements and compounds.

Mixture

A combination of two or more substances not chemically bonded.

Homogeneous Mixture

A mixture with uniform composition throughout (e.g., salt water).

Heterogeneous Mixture

A mixture with visibly different parts (e.g., salad).

Solution

A homogeneous mixture where one substance dissolves in another.

Diatomic Elements

Elements that exist as two atoms

Chemical Formula

Shows the types and numbers of atoms in a compound.

Structural Formula

Shows how atoms are bonded in a molecule.

Molecular Formula

Actual number of atoms in a molecule.

Empirical Formula

Simplest whole-number ratio of atoms in a compound.

Law of Definite Proportions

A compound always contains the same proportion of elements by mass.

Law of Multiple Proportions

Elements can combine in different ratios to form different compounds.

Chemical Change

A change that produces new substances (e.g., rusting).

Physical Change

A change that does not alter the chemical identity (e.g., melting).

Density

Mass per unit volume; Density = Mass / Volume.

Intensive Property

Does not depend on amount (e.g., density, boiling point).

Extensive Property

Depends on amount (e.g., mass, volume).

Phase Change

Transition between states of matter (e.g., melting, boiling).

Significant Figures

Digits that carry meaning in a measurement.

Accuracy

How close a measurement is to the true value.

Precision

How close repeated measurements are to each other.

Proton

Positively charged particle in the nucleus.

Neutron

Neutral particle in the nucleus.

Electron

Negatively charged particle orbiting the nucleus.

Isotope

Same element, different number of neutrons.

Ion

Atom with a charge due to loss/gain of electrons.

Isotope Symbol

Format

Alpha Radiation

Helium nucleus; low penetration, high mass.

Beta Radiation

Electron; moderate penetration.

Gamma Radiation

Electromagnetic wave; high penetration, no mass.

Gold Foil Experiment

Rutherford's experiment showing nucleus is small and dense.

Cathode Ray Experiment

Thomson discovered the electron.

Oil Drop Experiment

Millikan measured the charge of an electron.

Dalton's Postulates

Early atomic theory

Periodic Table Groups

Vertical columns; elements share properties.

Periodic Table Periods

Horizontal rows; elements have same energy levels.

Metals

Conductive, malleable, shiny; left side of table.

Nonmetals

Poor conductors, brittle; right side of table.

Metalloids

Properties of both metals and nonmetals; staircase line.

Alkali Metals

Group 1; very reactive, 1+ charge.

Alkaline Earth Metals

Group 2; reactive, 2+ charge.

Halogens

Group 17; reactive nonmetals, 1− charge.

Noble Gases

Group 18; inert gases, no charge.

Oxidation Number

Charge of an atom in a compound; based on group.

Ionic Formula

Balanced formula with charges canceling out.

Mass Spectrometer

Device that separates isotopes by mass.

Mass Spectrum

Graph showing isotope abundance vs. mass.

Factor-Label Method

Dimensional analysis using conversion factors.

Density Lab

Use mass and volume to calculate density.

Chemical Property

Describes ability to undergo chemical change.

Physical Property

Observable without changing identity.

Nitrate

NO₃⁻

Charge of Nitrate

-1

Nitrite

NO₂⁻

Charge of Nitrite

-1

Sulfate

SO₄²⁻

Charge of Sulfate

-2

Sulfite

SO₃²⁻

Charge of Sulfite

-2

Carbonate

CO₃²⁻

Charge of Carbonate

-2

Phosphate

PO₄³⁻

Charge of Phosphate

-3

Phosphite

PO₃³⁻

Charge of Phosphite

-3

Hydroxide

OH⁻

Charge of Hydroxide

-1

Chlorate

ClO₃⁻

Charge of Chlorate

-1

Chlorite

ClO₂⁻

Charge of Chlorite

-1

Hypochlorite

ClO⁻

Charge of Hypochlorite

-1

Perchlorate

ClO₄⁻

Charge of Perchlorate

-1

Hypo- Prefix

Indicates one fewer oxygen than -ite.

Per- Prefix

Indicates one more oxygen than -ate.

-ite Suffix

Indicates one fewer oxygen than -ate.

-ate Suffix

Indicates more oxygen than -ite.