Campbell biology chapter 2 12th edition

Matter

Anything that has mass and takes up space

Element

A substance that cannot be broken down into simpler substances

Compound

substance formed by the chemical combination of two or more elements in definite proportions

essential elements

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

trace elements

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

Atoms

smallest unit of matter

Nuetrons

Neutral particles that don't have an electric charge

Protons

Positively charged particles

Electrons

Negatively charged particles

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

Atomic mass

The average mass of all the isotopes of an element

Isotopes

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.

half-life

length of time required for half of the radioactive atoms in a sample to decay

radioactive isotope

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

radiometric dating

method used to determine the age of rocks using the rate of decay of radioactive isotopes

Energy

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

potential energy

stored energy that results from the position or shape of an object

electron shell

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

valence electrons

The electrons in the outermost shell (main energy level) of an atom; these are the electrons involved in forming bonds.

valence shell

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

Chemical bonds

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 bond formed when atoms share one or more pairs of electrons

Molecule

two or more atoms held together by covalent bonds

single bond

a covalent bond in which one pair of electrons is shared between two atoms

double bond

A covalent bond in which two pairs of electrons are shared between two atoms

Valence

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

Electronegativety

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

non polar covalent bond

a covalent bond in which the bonding electrons are shared equally by the bonded atoms, resulting in a balanced distribution of electrical charge

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.

Ions

positively and negatively charged atoms

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

composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal

hydrogen bond

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.

vaan der waals interactions

attractions between molecules that are close together as a result of these charges

chemical reaction

the process by which one or more substances change to produce one or more different substances

Reactant

a substance that takes part in and undergoes change during a reaction.

Products

The elements or compounds produced by 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 with time.

Orbitals

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