Biology Chapter 2

Anything that occupies space and has mass.

A substance that cannon be broken down into other substances by ordinary means.

A substance containing two or more elements in a fixed ratio.

A subatomic particle with a single positive electrical charge, found in the nucleus of an atom.

A subatomic particle with a single negative charge.

A subatomic particle that is electrically neutral.

An atom's central core, containing protons and neutrons.

The number of protons in each atom of a particular element.

The approximate total mass of an atom; alos called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number.

The sum of the number of protons and neutrons in an atom's nucleus.

A variant form of an atom. Isotopes of an element have the same number of protons, but different numbers of neutrons.

An isotope whose nucleus decays spontaneously, giving off particles and energy.

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

An attraction between two atoms resulting from a sharing outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.

An atom or molecule that has gained or lost one or more electrons, thus acquiring an electrical charge.

An attraction between two ions with opposite electrical charges. The electrical attraction of the opposite charges holds the ions together.

A compound resulting from the formation of ionic bonds; also called an ionic compound.

An attraction between atoms that share one or more pairs of outer-shell electrons; symbolized by a single line between the atoms.

A group of two or more atoms held together by covalent bonds.

A type of covalent bond in which two atoms share pairs of electrons; symbolized by a pair of lines between the bonded atoms.