Honors Chemistry Vocabulary

Matter

Anything that occupies space and has mass; the physical material of the universe.

Property

A characteristic that gives a sample of matter its unique identity.

Element

A substance that cannot be separated into simpler substances by chemical means.

Atom

The smallest representative particle of an element.

Molecule

A chemical combination of two or more atoms.

States of Matter

The three forms that matter can assume: solid, liquid, and gas.

Gas

Matter that has no fixed volume or shape; it conforms to the volume and shape of its container.

Liquid

Matter that has a distinct volume but no specific shape.

Solid

Matter that has both a definite shape and a definite volume.

Pure Substance

Matter that has a fixed composition and distinct properties.

Compound

A substance compose of two or more elements united chemically in definite proportions.

Mixture

A combination of two or more substances in which each substance retains its own chemical identity.

Heterogeneous Mixture

A mixture which does not have the same composition, properties, and appearance throughout.

Homogeneous Mixture

A mixture which has uniform composition, properties, and appearance throughout.

Solution

A mixture of substances that has a uniform composition; a homogeneous mixture.

Physical Properties

Properties that can be measured without changing the composition of a substance, for example, color and freezing point.

Chemical Properties

Properties that describe a substance's composition and its reactivity; how the substance reacts and changes into other substances.

Physical Change

Changes, such as phase change, that occur with no change in chemical composition.

Changes of State

Transformations of matter from one state to a different one, for example, from a gas to a liquid.

Chemical Reaction

Processes in which one or more substances are converted into other substances; also called chemical changes.

SI Units

The preferred metric units for use in science: kilogram, meter, second, kelvin, mole, ampere, candela.

Mass

A measure of the amount of material in an object. It measures the resistance of an object to being moved. In SI units, mass is measured in kilograms.

Temperature

directly proportional to the average kinetic energy of the particles. In solids proportional to the vibrational energy.

Celsius Scale

A temperature scale on which water freezes at 0 degrees and boils at 100 degrees at sea level.

Kelvin Scale

The absolute temperature scale; the SI unit for temperature.

Absolute Zero

The coldest temperature, 0 Kelvin, that can be reached. It is the hypothetical temperature at which all molecular motion stops.

Density

The ratio of an object's mass to its volume.

Precision

The closeness of agreement among several measurements of the same quantity; the reproducibility of a measurement.

Accuracy

A measure of how closely individual measurements agree with the correct value.

Significant Figures

The digits that indicate the precision with which a measurement is made; all digits of a measured quantity are significant, including the last digit, which is uncertain.

Dimensional Analysis

A method of problem solving in which units are carried through all calculations, ensuring the correct final units.

Conversion Factor

A ratio relating the same quantity in two systems of units that is used to convert the units of measurement.

Law of Conservation of Mass

A scientific law stating that the total mass of the products of a chemical reaction is the same as the total mass of the reactants, so that the mass remains constant during the reaction.

Subatomic Particles

Particles such as protons, neutrons, and electrons that are smaller than an atom.

Radioactivity

The process in which an unstable atomic nucleus emits charged particles and energy.

Nucleus

The very small, very dense positively charged portion of the atom; it is composed of protons and neutrons.

Proton

A positively charged subatomic particle found in the nucleus of the atom.

Neutron

An electrically neutral particle found in the nucleus of an atom; it has approximately the same mass as a proton.

Electron

A negatively charged subatomic particle found outside the atomic nucleus; it is a part of all atoms and has 1/1836 the mass of a proton.

Electronic Charge

The negative charged carried by an electron; it has a magnitude of 1.602 x 10^-19 C.

Atomic Mass Unit (amu)

A unit based on the value of exactly 12 amu for the mass of an isotope of carbon that has six protons and six neutrons in the nucleus.

Atomic Number

The number of protons in the nucleus of an atom of an element.

Mass Number

The sum of the number of protons and neutrons in the nucleus of a particular atom.

Atomic Weight

The average mass of the atoms of an element in atomic mass units (amu); it is numerically equal to the mass in grams of one mole of the element.

Mass Spectrometer

An instrument used to measure the precise masses and relative amounts of atomic and molecular ions.

Periodic Table

The arrangement of elements in order of increasing atomic number, with elements having similar properties placed in vertical columns.

Period

The row of elements that lie in a horizontal row in the periodic table.

Group

Elements that are in the same column of the periodic table; elements within the same group or family exhibit similarities in their chemical behavior.

Metal

Elements that are usually solids at room temperature, exhibit high electrical and heat conductivity, and appear lustrous.

Nonmetal

Elements in the upper right corner of the periodic table; nonmetals differ from metals in their physical and chemical properties.

Metalloid

Elements that lie along the diagonal line separating the metals from the nonmetals in the periodic table; the properties of which are intermediate between those of metals and nonmetals.

Chemical Formula

A notation that uses chemical symbols and numerical subscripts to convey the relative proportions of atoms of the different elements in a substance.

Diatomic Molecule

A molecule composed of only two atoms.

Molecular Compounds

A compound that consists of molecules. Water for example

Molecular Formula

A chemical formula that indicates the actual number of atoms of each element in one molecule of a substance.

Empirical Formula

A chemical formula that shows the kinds of atoms and their relative numbers in a substance in the smallest possible whole-number ratios.

Structural Formula

A formula that shows not only the number and kinds of atoms in the molecule but also the arrangement of bonds of the atoms.

Ion

An electrically charged atom or group of atoms (polyatomic ion); ions can be positively or negatively charged, depending on whether electrons are lost or gained by atoms.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Polyatomic Ion

An electrically charged group of two or more atoms.

Ionic Compound

A compound composed of cations and anions.

Oxyanion

A polyatomic ion that contains one or more oxygen atoms.

Organic Chemistry

The study of carbon containing compounds, typically containing carbon-carbon bonds.

Hydrocarbons

Compounds composed of only carbon and hydrogen.

Quantum Theory

the theory that describes matter and energy at very small (atomic) sizes

Electromagnetic Radiation

a kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.

Wavelength

The distance between two corresponding parts of a wave

Frequency

the number of complete wavelengths that pass a point in a given time

Quantum

the minimum amount of energy that can be gained or lost by an electron

Photoelectric Effect

The emission of electrons from a metal when light shines on the metal

Photon

A particle of electromagnetic radiation with no mass that carries a quantum of energy

Spectrum

colored band produced when a beam of light passes through a prism. Can also refer to a range of values.. a range of wavelegnths or a wave of mass (mass spectrum)

Continuous Spectrum

most objects reflect a large variety of wavelengths of light

Line Spectrum

lines of specific wavelength released by excited electrons. Can be used to identify elements

Ground State

electrons in the most stable configuration. Lower energy

Excited State

atoms that have gained energy and have moved up to a higher energy level than the ground state. Excited electrons release photons as they return to the ground state

Probability Density

a value that represents the probability that an electron will be found at a given point in space

Electron Density

gives the probability that an electron will be found in a particular region of an atom

Orbital

a representation of the space occupied by an electron in an atom; the probability distribution for the electron

Electron Shell

An energy level representing the distance of an electron from the nucleus of an atom.

Subshell

A subdivision of an energy level in an atom. They are divided into orbitals. Examples s,p,d,f

Electron Spin

the clockwise or counterclockwise motion of an electron

Pauli Exclusion Principle

An atomic orbital may describe at most two electrons, each with opposite spin direction

Electron Configuration

the arrangement of electrons in the orbitals of an atom

Hund's Rule

electrons have opposite spin. electrons occupy single sub orbitals before they form pairs.

Core Electrons

The electrons that are not in the outermost shell of an atom.

Valence Electrons

Electrons on the outermost energy level of an atom

Transition Metals

Groups 3-12, 1-2 electrons in the outer energy level, less reactive than alkali-earth metals, shiny, good conductor of thermal energy and electrical current, high density

Lanthanide Elements

Elements 58-71

Actinide Elements

contains atomic numbers 89 to 103 referred to as Rare Earth Metals. These elements all have a high diversity in oxidation numbers and all are radioactive.

F-Block Metals

lanthanides and actinides and are called the inner transition elements because of their placement in the periodic table due to their electron configurations

All Electrons

Core + Valence