Chapter 2

Front 1

matter

Back 1

anything that takes up space

Front 2

element

Back 2

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

Front 3

compound

Back 3

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

Front 4

essential elements

Back 4

elements an organism needs to live a healthy life and reproduce

Front 5

trace elements

Back 5

elements required by an organism in only minute quantities

Front 6

atom

Back 6

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

Front 7

proton

Back 7

positively charged

Front 8

electron

Back 8

negatively charged

Front 9

neutron

Back 9

neutral charged; determines isotope

Front 10

atomic nucleus

Back 10

dense core, made up of protons and neutrons, at the center of the atom

Front 11

dalton

Back 11

atomic mass unit, or amu

Front 12

atomic number

Back 12

number of protons, unique to the atom

Front 13

mass number

Back 13

sum of protons plus neutrons in the nucleus of an atom

Front 14

atomic mass

Back 14

the total mass of an atom, numerically equivalent to the mass in grams of 1 mole of the atom

Front 15

isotope

Back 15

one of several atomic forms of an element,each with the same number of protons but a different number of neurons, thus different in atomic mass

Front 16

radioactive isotope

Back 16

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

Front 17

half-life

Back 17

the time it takes for 50% of the parent isotope to decay

Front 18

radiometric dating

Back 18

measuring the ratio of different isotopes and calculate how many half-lives (in years) have passed since an organism was fossilized or a rock was formed

Front 19

energy

Back 19

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

Front 20

potential energy

Back 20

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

Front 21

valence electron

Back 21

an electron in the outermost shell

Front 22

valence shell

Back 22

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

Front 23

orbital

Back 23

the 3D space where an electron is found 90% of the time

Front 24

chemical bond

Back 24

an attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence out opposite charges on the atoms; the bonded atoms gain complete outer electron shells

Front 25

covalent bond

Back 25

a type of strong chemical bonds in which two atoms share one or more pairs of valence electrons

Front 26

molecule

Back 26

two or more atoms held together by covalent bonds

Front 27

single bond

Back 27

a single covalent bond; the Sharon's of a pastor of valence electrons by two atoms

Front 28

double bond

Back 28

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

Front 29

valence

Back 29

the bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atom's outermost (valence) shell

Front 30

electronegativity

Back 30

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

Front 31

nonpolar covalent bond

Back 31

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

Front 32

polar covalent bond

Back 32

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

Front 33

ion

Back 33

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

Front 34

cation

Back 34

a positively charged ion

Front 35

anion ion

Back 35

a negatively charged

Front 36

ionic bond

Back 36

a chemical bond resulting from the attraction between positively charged ions

Front 37

ionic compound

Back 37

a compound resulting from the foundation of an ionic bond; also called a salt

Front 38

hydrogen bond

Back 38

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

Front 39

van der Waals interactions

Back 39

weak attractions between molecules or pays that result from transient local partial charges

Front 40

chemical reactions

Back 40

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

Front 41

reactant

Back 41

a starting material in a chemical reaction

Front 42

product

Back 42

a material resulting from a chemical reaction

Front 43

chemical equilibrium

Back 43

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