Unit 0, Chapter 2

Question 1

matter

Answer 1

anything that takes up space and has mass

Question 2

element

Answer 2

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

Question 3

compound

Answer 3

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

Question 4

essential elements

Answer 4

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

Question 5

trace elements

Answer 5

an element indispensable for life but required in extremely minute amounts

Question 6

atom

Answer 6

the smallest unit of matter than retains the properties of an element

Question 7

neutrons

Answer 7

a subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 x 10^-24g, found in the nucleus of an atom

Question 8

protons

Answer 8

a subatomic particle with a single positive electrical charge, with a mass of about 1.7 x 10^-24g, found in the nucleus of an atom

Question 9

electrons

Answer 9

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 electron move around the nucleus of an atom

Question 10

atomic nucleus

Answer 10

an atom’s dense central core, containing protons and neutrons

Question 11

dalton

Answer 11

a measure of mass for atoms and subatomic particles; the same as the atomic mass unit (amu)

Question 12

atomic number

Answer 12

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

Question 13

mass number

Answer 13

the total number of protons and neutrons in an atom’s nucleus

Question 14

atomic mass

Answer 14

the total mass of an atom, numerically equivalent to the mass in grams of 1 mole of the atom (for an element with more than one isotope, the atomic mass is the average mass of the naturally occuring isotopes, weighted by their abundance)

Question 15

isotope

Answer 15

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

Question 16

radioactive isotope

Answer 16

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

Question 17

half-life

Answer 17

the amount of time it takes for 50% of a sample of a radioactive isotope to decay

Question 18

radiometric dating

Answer 18

a method for determining the absolute age of rocks and fossils, based on the half-life of radioactive isotopes

Question 19

energy

Answer 19

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

Question 20

potential energy

Answer 20

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

Question 21

electron shells

Answer 21

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

Question 22

valence electrons

Answer 22

an electron in the outermost electron shell

Question 23

valence shell

Answer 23

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

Question 24

orbital

Answer 24

the three-dimensional (3D) space where an electron is found 90% of the time

Question 25

chemical bonds

Answer 25

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 (octet)

Question 26

covalent bond

Answer 26

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

Question 27

molecule

Answer 27

two or more atoms held together by covalent bonds

Question 28

single bond

Answer 28

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

Question 29

double bond

Answer 29

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

Question 30

valence

Answer 30

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

Question 31

electronegativity

Answer 31

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

Question 32

nonpolar covalent bond

Answer 32

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

Question 33

polar covalent bond

Answer 33

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

Question 34

ions

Answer 34

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

Question 35

cation

Answer 35

a positively charged ion

Question 36

anion

Answer 36

a negatively charged ion

Question 37

ionic bond

Answer 37

a chemical bond resulting from the attraction between oppositely charged ions

Question 38

ionic compounds

Answer 38

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

Question 39

salts

Answer 39

another term for an ionic compound (for definiton, see card 38: ionic compound)

Question 40

hydrogen bond

Answer 40

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

Question 41

van der Waals interactions

Answer 41

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

Question 42

chemical reactions

Answer 42

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

Question 43

reactants

Answer 43

a starting material in a chemical reaction (always on the left side)

Question 44

products

Answer 44

a material resulting from a chemical reaction (always on the right side)

Question 45

chemical equilibrium

Answer 45

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