AP Bio Chapter 2

Anything that takes up space and has mass.

Any substance that cannot be broken down to any other substance by chemical reactions.

A substance consisting of two or more different elements combined in a fixed ratio.

A chemical element required for an organism to survive, grow, and reproduce.

An element indispensable for life but required in extremely minute amounts.

The smallest unit of matter than retains the properties of an element.

A subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 times ten to the negative 24 g, found in the nucleus.

A subatomic particle with a single positive electrical charge, with a mass of about 1.7 times ten to the negative 24 g, found in the nucleus of an atom.

A subatomic particle with a single negative electrical charge and a mass about 1 two-thousandths that of a neutron or proton. One or more electrons move around the nucleus of an atom.

An atom’s dense core, containing protons and neutrons.

A measure for mass and subatomic particles; the same as the atomic mass unit, or amu.

The number of protons in the nucleus of an atom, unique for each element and designated by a subscript.

The total number of protons and neutrons in an atom’s nucleus.

The total mass of an atom, equivalent to the mass in grams of 1 mole of the atom. (For an element with more than one isotope, the atomic mass is the average mass of the naturally occurring isotopes, weighted by their abundance.)

One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass.

An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.

The amount of time it takes for 50 percent of a sample of a radioactive isotope to decay.

A method for determining the absolute age of rocks and fossils, based on the half-life of radioactive isotopes.

The capacity to cause change, especially to do work (to move matter against an opposing force).

The energy that matter possesses as a result of its location or spatial arrangement (structure).

An energy level of electrons at a characteristic average distance from the nucleus of an atom.

An electron in the outermost electron shell.

The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.

The three-dimensional space when an electron is found 90% of the time.

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

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.

Two or more atoms held together by covalent bonds.

Single covalent bond; the sharing of a pair of valence electrons by two atoms.

A double covalent bond; the sharing of two pairs of valence electrons by two atoms.

The bonding capacity of a given atom; the number of covalent bonds an atom can form, which usually equals the number of unpaired electrons in its outermost (valence) shell.

The attraction of a given atom for the electrons of a covalent bond.

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.

An atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge.

A positively charged ion.

A negatively charged ion.

A chemical bond resulting from the attraction between oppositely charged ions.

A compound resulting from the formation of an ionic bond; also called a salt.

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

A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.

Weak attractions between molecules or parts of molecules that result from transient local partial changes.

The making and breaking of chemical bonds, leading to changes in the composition of matter.

The starting material in a chemical reaction.

A material resulting from a chemical reaction.

In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time.