Chapter 2 Key Terms

Question 1

anion

Answer 1

A negatively charged ion.

Question 2

atom

Answer 2

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

Question 3

atomic mass

Answer 3

The total mass of an atom, which is the mass in grams of one mole of the atom.

Question 4

atomic nucleus

Answer 4

An atom’s central core, containing protons and neutrons.

Question 5

atomic number

Answer 5

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.

Question 6

cation

Answer 6

An ion with a positive charge, produced by the loss of one or more electrons.

Question 7

chemical bond

Answer 7

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.

Question 8

chemical equilibrium

Answer 8

In a reversible chemical reaction, the point at which the rate of the forward reaction equals the rate of the reverse reaction.

Question 9

chemical reaction

Answer 9

A process leading to chemical changes in matter; involves the making and/or breaking of chemical bonds.

Question 10

compound

Answer 10

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

Question 11

covalent bond

Answer 11

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

Question 12

dalton

Answer 12

A measure of mass for atoms and subatomic particles.

Question 13

electron

Answer 13

A subatomic particle with a single negative charge. One or more electrons move around the nucleus of an atom.

Question 14

electron shell

Answer 14

An energy level represented as the distance of an electron from the nucleus of an atom.

Question 15

electronegativity

Answer 15

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

Question 16

element

Answer 16

Any substance that cannot be broken down to any other substance.

Question 17

energy

Answer 17

The capacity to do work (to move matter against an opposing force).

Question 18

energy level

Answer 18

Any of several different states of potential energy for electrons in an atom.

Question 19

hydrogen bond

Answer 19

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.

Question 20

ion

Answer 20

An atom that has gained or lost electrons, thus acquiring a charge.

Question 21

ionic bond

Answer 21

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

Question 22

ionic compound

Answer 22

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

Question 23

isotope

Answer 23

One of several atomic forms of an element, each containing a different number of neutrons and thus differing in atomic mass.

Question 24

mass number

Answer 24

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

Question 25

matter

Answer 25

Anything that takes up space and has mass.

Question 26

molecular formula

Answer 26

A type of molecular notation indicating only the quantity of the constituent atoms.

Question 27

molecule

Answer 27

Two or more atoms held together by covalent bonds.

Question 28

neutron

Answer 28

An electrically neutral particle (a particle having no electrical charge), found in the nucleus of an atom.

Question 29

nonpolar covalent bond

Answer 29

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

Question 30

orbital

Answer 30

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

Question 31

periodic table of elements

Answer 31

A chart of the chemical elements, arranged in three rows, corresponding to the number of electron shells in their atoms.

Question 32

polar covalent bond

Answer 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.

Question 33

potential energy

Answer 33

The energy stored by matter as a result of its location or spatial arrangement.

Question 34

product

Answer 34

An ending material in a chemical reaction.

Question 35

proton

Answer 35

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

Question 36

radioactive isotope

Answer 36

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

Question 37

reactant

Answer 37

A starting material in a chemical reaction.

Question 38

salt

Answer 38

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

Question 39

structural formula

Answer 39

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

Question 40

trace element

Answer 40

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

Question 41

valence

Answer 41

The bonding capacity of an atom, generally equal to the number of unpaired electrons in the atom’s outermost shell.

Question 42

valence electron

Answer 42

An electron in the outermost electron shell.

Question 43

valence shell

Answer 43

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

Question 44

van der Waals interactions

Answer 44

Weak attractions between molecules or parts of molecules that are brought about by localized charge fluctuations.