The smallest unit of matter that retains the properties of an element.
The total mass of an atom, which is the mass in grams of one mole of the atom.
An atom’s central core, containing protons and neutrons.
The number of protons in the nucleus of an atom, unique for each element and designated by a subscript to the left of the elemental symbol.
An ion with a positive charge, produced by the loss of one or more electrons.
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 electron shells.
In a reversible chemical reaction, the point at which the rate of the forward reaction equals the rate of the reverse reaction.
A process leading to chemical changes in matter; involves the making and/or breaking of chemical bonds.
A substance consisting of two or more elements in a fixed ratio.
A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.
A measure of mass for atoms and subatomic particles.
A subatomic particle with a single negative charge. One or more electrons move around the nucleus of an atom.
An energy level represented as the distance of an electron from the nucleus of an atom.
The attraction of an atom for the electrons of a covalent bond.
Any substance that cannot be broken down to any other substance.
The capacity to do work (to move matter against an opposing force).
Any of several different states of potential energy for electrons in an atom.
A type of weak chemical bond 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.
An atom that has gained or lost electrons, thus acquiring a charge.
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.
One of several atomic forms of an element, each containing a different number of neutrons and thus differing in atomic mass.
The sum of the number of protons and neutrons in an atom’s nucleus.
Anything that takes up space and has mass.
A type of molecular notation indicating only the quantity of the constituent atoms.
Two or more atoms held together by covalent bonds.
An electrically neutral particle (a particle having no electrical charge), found in the nucleus of an atom.
nonpolar covalent bond
A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
The three-dimensional space where an electron is found 90% of the time.
periodic elements of the table
A chart of the chemical elements, arranged in three rows, corresponding to the number of electron shells in their atoms.
polar covalent bond
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.
The energy stored by matter as a result of its location or spatial arrangement.
An ending material in a chemical reaction.
A subatomic particle with a single positive electrical charge, found in the nucleus of an atom.
An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.
A starting material in a chemical reaction.
A compound resulting from the formation of an ionic bond; also called an ionic compound.
A type of molecular notation in which the constituent atoms are joined by lines representing covalent bonds.
An element indispensable for life but required in extremely minute amounts.
The bonding capacity of an atom, generally equal to the number of unpaired electrons in the atom’s outermost shell.
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.
van der Waals interactions
Weak attractions between molecules or parts of molecules that are brought about by localized charge fluctuations.