Chemistry Midterm

Mass

the amount of matter in an object

Matter

Anything that has mass and takes up space

Weight

A measure of the gravitational force exerted on an object.

Formula for density

D=m/v

Atomic Theory

Concept explaining matter is made of atoms.

Democritus

Proposed all matter consists of indivisible particles.

John Dalton

Introduced atomic theory with unique indivisible atoms.

J.J. Thomson

Discovered electrons using a cathode ray tube.

Plum Pudding Model

Electrons embedded in positively charged sphere.

Ernest Rutherford

Discovered atomic nucleus via gold foil experiment.

Niels Bohr

Proposed electrons orbit nucleus in energy levels.

Quantum Mechanical Model

Describes electrons as wave-like particles.

Nucleus

Dense center of atom, contains protons and neutrons.

Protons

Positively charged particles in the nucleus.

Neutrons

Neutral particles in the nucleus, contribute to mass.

Electrons

Negatively charged particles in constant motion.

Electron Cloud

Space around nucleus filled with moving electrons.

Energy Levels

Regions where electrons reside at varying energies.

Valence Electrons

Electrons in outermost shell with highest energy.

Metal Staircase

Line separating metals and nonmetals on periodic table.

Groups

Vertical columns in the periodic table.

Periods

Horizontal rows in the periodic table.

Shells

Regions of space around nucleus for electrons.

Mass of Atom

Most mass located in the nucleus.

Electron Motion

Electrons are in constant motion within the cloud.

Nuclear Chemistry

Study of atomic nucleus and its transformations.

Radiation

Energy emitted from unstable atomic nuclei.

Alpha Radiation

Emission of helium nuclei from radioactive atoms.

Beta Radiation

High-energy electrons emitted from radioactive decay.

Gamma Radiation

High-energy electromagnetic radiation from nuclear reactions.

Fission

Process of splitting a large atom into smaller ones.

Fusion

Process of combining lighter atoms into a heavier one.

Half-Life

Time required for half of a radioactive substance to decay.

Democritus

Contributed the idea of the first atomic theory in 400 BC.

Niels Bohr

Proposed the Bohr Model in 1913.

John Dalton

Formulated the first atomic theory in 1803.

J.J. Thompson

Developed the Plum Pudding Model in 1897.

Schrödinger + Heisenberg

Contributed to the Electron Cloud Model in 1927.

Ernest Rutherford

Proposed the Nuclear Model in 1911.

Atom

The smallest unit of an element that retains the properties of that element.

Carbon-12 and Carbon-14

Differ in mass number.

Density

Mass per unit volume of a substance.

Extensive Properties

Properties dependent on the amount of matter.

Intensive Properties

Properties independent of the amount of matter.

Chemical Properties

Characteristics that determine substance's chemical behavior.

Physical Properties

Characteristics observable without changing substance's identity.

Independent Variables

Factors manipulated in an experiment to test effects.

Dependent Variables

Factors measured in response to independent variables.

Claim, Evidence, Reasoning

Framework for scientific argumentation and explanation.

Hypotheses

Testable predictions based on observations.

Qualitative Observations

Descriptive data without numerical measurement.

Quantitative Observations

Data expressed in numerical terms.

Unit Conversions

Process of converting one measurement unit to another.

Significant Figures

Digits in a number that carry meaningful information.

Scientific Notation

Method of expressing numbers as a product of powers.

Volume

The amount of space an object takes up