Chemical Context of Life Vocabulary

Anion

A negatively charged ion

Atom

The smallest unit of matter that retains the properties of an element

Atomic Nucleus

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

Atomic Number

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

Atomic Weight

the total weight of an atom

Cation

A positively charged ion.

Chemical Bond

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.

Chemical Equilibrium

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.

Chemical Reaction

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

Compound

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

Covalent Bond

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

Double Bond

the sharing of two pairs of valence electrons by two atoms.

Electron Shell

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

Electron

A subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or proton. One or more electrons move around the nucleus of an atom.

Electronegativity

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

Element

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

Energy Level

fixed distances from the nucleus of an atom where electrons may be found.

Energy

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

Hydrogen Bond

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

Ion

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

Adhesion

The clinging of one substance to another, such as water to plant cell walls, by means of hydrogen bonds.

Kinetic Energy

The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter

Polar Molecule

A molecule (such as water) with an uneven distribution of charges in different regions of the molecule.

Solute

A substance that is dissolved in a solution.

Solution

A liquid that is a homogeneous mixture of two or more substances

Solvent

The dissolving agent of a solution. Water is the most versatile solvent known.

Specific Heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C.

Hydrophilic

Having an affinity for water.

Hydrophobic

Having no affinity for water; tending to coalesce and form droplets in water.

Ionic Bond

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

Ionic Compound

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

Isotope

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.

Mass Number

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

Matter

Anything that takes up space and has mass.

Molecule

Two or more atoms held together by covalent bonds

Neutron

A subatomic particle having no electrical charge (electrically neutral), with a mass of GLOSSARY G-20 GLOSSARY about 1.7 3 10224 g, 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.

Potential Energy

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

Product

A material resulting from a chemical reaction.

Proton

A subatomic particle with a single positive electrical charge, with a mass of about 1.7 3 10224 g, found in the nucleus of an atom.

Radioactive Isotope

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

Reactant

A starting material in a chemical reaction.

Salt

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

Trace Element

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

Valence Electron

An electron in the outermost electron shell.

Valence Shell

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

Valence

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.

Van der Waals Interactions

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

pH

A measure of hydrogen ion concentration equal to -log [H1] and ranging in value from 0 to 14.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid.

Temperature

Cohesion

The linking together of like molecules, often by hydrogen bonds.

Evaporative Cooling

The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state.

Heat of Vaporization

The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state

Hydrogen Ion

A single proton with a charge of 11. The dissociation of a water molecule (H2O) leads to the generation of a hydroxide ion (OH2) and a hydrogen ion (H1); in water, H1 is not found alone but associates with a water molecule to form a hydronium ion.