Unit 3 flash cards Phyisical Sceince

Chemical reaction

a rearrangement of atoms into new combinations

Compounds

Substances composed of two or more elements in fixed proportions

Nucleus

The extremely small, positively charged, dense center of an atom that contains positively charged protons, neutral neutrons, and is surrounded by empty space through which one or more negatively charged electrons move.

Proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom.

Neutron

A subatomic particle that has no charge and that is found in the nucleus of the atom.

Electron

A negatively charged particle that is found outside the nucleus of an atom.

Orbital

A region in an atom where there is a high probability of finding electrons.

Valence electron

An electron that is found in the outermost shell of an atom and that determines the atom's chemical properties.

Periodic law

The law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of elements.

Period

The elements in a horizontal row of the periodic table.

Group

A vertical column of elements in the periodic table (also called family) elements in a group share chemical properties.

Ion

An atom, radical, or molecule that has gained or lost one or more electrons and has a negative or positive charge.

Atomic number

The number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element.

Mass number

The sum of the numbers of protons and neutrons in the nucleus of an atom.

Isotope

An atom that has the same number of protons as other atoms of the same element do but that has a different number of neutrons.

Atomic mass unit (amu)

A unit of mass that describes the mass of an atom or molecule; it is exactly one-twelfth of the mass of a carbon atom with mass number 12 (abbreviation, amu).

Average atomic mass

The weighted average of the masses of all naturally occurring isotopes of an element.

Metal

A class of elements characterized by physical properties that include shininess, malleability, ductility, and conductivity.

Malleable

A term used to describe a material that can be pounded into shape.

Ductile

A term used to describe a material that can be pulled out into a long wire.

Conductivity

The ability of an object to transfer heat or electricity to another object.

Reactivity

The ease and speed with which an element combines, or reacts, with other elements and compounds.

Corrosion

The gradual wearing away of a metal element due to a chemical reaction.

Alkali metal

An element in Group 1 of the periodic table.

Alkaline earth metal

An element in Group 2 of the periodic table.

Transition metal

One of the elements in Groups 3 through 12 of the periodic table.

Radioactive decay

The process in which the atomic nuclei of unstable isotopes release fast-moving particles and energy.

Radioactivity

The spontaneous emission of radiation by an unstable atomic nuclei.

Alpha particle

A type of nuclear radiation consisting of two protons and two neutrons.

Beta particle

A fast-moving electron that is given off as nuclear radiation.

Gamma radiation

A type of nuclear radiation made of high energy waves.

Tracer

A radioactive isotope that can be followed through the steps of a chemical reaction or industrial process.

Nonmetal

An element that lacks most of the properties of metal.

Diatomic molecule

A molecule consisting of two atoms.

Halogen

An element found in Group 17 of the periodic table.

Noble gas

An element in Group 18 of the periodic table.

Metalloid

An element that has some characteristics of both metals and nonmetals.

Semiconductor

A material that conducts current under certain conditions.