Chem 20A Final Version

Intensive property

A physical property that does not depend on the amount of matter present such as temperature or density

Extensive property

A physical property that depends on the amount of matter present such as mass or volume

Law of Definite Proportions

A chemical compound always contains its component elements in fixed ratio by mass regardless of the size or source of the sample

Law of Multiple Proportions

When two elements form more than one compound the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers

Dalton’s Atomic Theory

States that all matter is composed of indivisible atoms that combine in simple whole number ratios to form compounds and that atoms of each element are identical in mass and properties

Avogadro’s Hypothesis

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules

Cathode Ray Experiment

Discovered electrons and determined that atoms contain negatively charged particles

Oil Drop Experiment

Determined the charge of an electron to be 1.60 × 10⁻¹⁹ coulombs

Gold Foil Experiment

Discovered the atomic nucleus and showed that atoms are mostly empty space

Mass Spectrometry

Discovered isotopes and allowed measurement of atomic masses

Photoelectric Effect

Demonstrated that light behaves as particles called photons which can eject electrons from metal surfaces

De Broglie Hypothesis

Proposed that matter exhibits wave particle duality and that electrons have a wavelength given by λ = h divided by mv

Bohr Model

Proposed quantized energy levels for electrons with energy given by Eₙ = −2.18 × 10⁻¹⁸ multiplied by Z² divided by n²

Quantum Numbers

A set of four numbers (n, l, mₗ, mₛ) that describe the energy state and spatial distribution of an electron

Principal Quantum Number n

Indicates the main energy level or shell of an electron

Angular Momentum Quantum Number l

Defines the shape of the orbital and ranges from 0 to n−1

Magnetic Quantum Number mₗ

Describes the orientation of an orbital in space and ranges from −l to +l

Spin Quantum Number mₛ

Describes the spin of an electron with possible values of +½ or −½

s orbital

Spherical shape with zero angular nodes

p orbital

Dumbbell shape with one angular node

d orbital

Cloverleaf shape with two angular nodes

f orbital

Complex shape with three angular nodes

Nodes

Regions where the probability of finding an electron is zero

Effective Nuclear Charge

The net positive charge experienced by an electron due to shielding from inner electrons

Shielding

The reduction in effective nuclear charge felt by outer electrons due to repulsion by inner electrons

Aufbau Principle

Electrons occupy the lowest energy orbitals first

Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers

Hund’s Rule

Electrons occupy degenerate orbitals singly before pairing up

Electron Configuration

The arrangement of electrons in an atom following the rules of Aufbau Pauli and Hund

Blackbody Radiation

Emission of light by an object as it is heated demonstrating quantized energy levels

Photon Energy Equation

E = hν = hc divided by λ where h is Planck’s constant and c is the speed of light

Planck’s Constant

A fundamental constant h = 6.626 × 10⁻³⁴ J·s

Speed of Light

c = 3.00 × 10⁸ m/s in a vacuum

Photoelectric Equation

E photon = Φ + KE electron where Φ is work function

Rydberg Equation

1 divided by λ = R multiplied by (1 divided by n₁² minus 1 divided by n₂²) for spectral lines of hydrogen

Rydberg Constant

R = 1.097 × 10⁷ m⁻¹

De Broglie Equation

λ = h divided by mv describes wave behavior of matter

Mole

The amount of substance that contains 6.022 × 10²³ representative particles

Avogadro’s Number

6.022 × 10²³ particles per mole

Molar Mass

The mass of one mole of a substance expressed in grams per mole

Empirical Formula

The simplest whole number ratio of elements in a compound

Molecular Formula

The actual number of atoms of each element in a molecule

Stoichiometry

The quantitative relationship between reactants and products in a chemical reaction

Law of Conservation of Mass

Matter cannot be created or destroyed in a chemical reaction

Isotopes

Atoms of the same element with different numbers of neutrons

Atomic Mass

The weighted average mass of all naturally occurring isotopes of an element

Ground State

The lowest energy state of an atom

Excited State

Any energy level higher than the ground state where electrons have absorbed energy

Energy Transition

When an electron moves between levels it absorbs or emits energy equal to ΔE = E final minus E initial

Wavelength and Frequency Relationship

c = λν where c is the speed of light λ is wavelength and ν is frequency

Wave Particle Duality

Concept that all matter exhibits both wave like and particle like properties

Spectroscopy

The study of the interaction between matter and electromagnetic radiation

Electron Affinity

The energy change when an electron is added to a neutral atom

Ionization Energy

The energy required to remove an electron from an atom in its gaseous state

Periodic Trend of Ionization Energy

Increases across a period and decreases down a group

Periodic Trend of Atomic Radius

Decreases across a period and increases down a group

Periodic Trend of Electron Affinity

Becomes more negative across a period and less negative down a group