Chemistry of Life

Matter

Anything that takes up space and has mass; is made up of elements.

Element

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

Compound

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

Emergent Property of a Compound

A compound has characteristics different from those of its elements. Example: The metal sodium combines with the poisonous gas chlorine, forming the edible compound sodium chloride, or table salt.

Four Most Common Elements in Living Matter

Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N)

Trace Element

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

Atom

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

Subatomic Particles

Atoms are composed of these even smaller parts.

Neutron

A subatomic particle having no electrical charge, found in the nucleus of an atom.

Proton

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

Electron

A subatomic particle with a single negative electrical charge that moves around the nucleus of an atom.

Atomic Nucleus

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

Dalton

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

Atomic Number

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.

Mass Number

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

How to Calculate the Number of Neutrons

Atomic mass (subscript) - Atomic Number (superscript)

Atomic Mass

An approximation of the total mass of neutrons and protons of an atom.

Isotope

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

Radioactive Isotope

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

Energy

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

Potential Energy

The energy that matter posesses as a result of its location or spatial arrangement (structure). Example: Water in a reservoir on a hill has more of it because of its altitude.

Electron Shell

An energy level of electrons at a characteristic average distance from the nucleus of an atom. Example: Sunlight excites them in the surface of a car to higher energy levels.

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.

Orbital

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

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.

Covalent Bond

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

Molecule

Two or more atoms held together by covalent bonds.

Single Bond

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

Structural Formula

A type of molecular notation in which the constituent atoms are joined by lines representing covalent bonds. H--H

Molecular Formula

A type of molecular notation representing the quantity of constituent atoms, but not the nature of the bonds that join them. H2

Double Bond

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

Valence

The bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atoms's outermost shell.

Electronegativity

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

Nonpolar Covalent Bond

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

Polar Covalent Bond

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

Ion

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

Cation

A positively charged ion.

Anion

A negatively charged ion.

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.

Salt

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

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 of a polar covalent bond in ano

van der Waals Interactions

Weak attractions between molecules or parts of molecules that result from localized charge fluctuations.

Chemical Reaction

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

Reactant

A starting material in a chemical reaction.

Product

A material resulting from a chemical reaction.

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 wit