Chapter 2: Atoms, Molecules, and Ions

Question 1

law of definite proportions

Answer 1

different samples of the same compound always contain its constituent elements in the same proportion by mass

Question 2

law of multiple proportions

Answer 2

if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers

Question 3

law of conservation of mass

Answer 3

matter can be neither created nor destroyed

matter is made of atoms that are unchanged in a chemical reaction; mass must be conserved as well

Question 4

atom

Answer 4

the basic unit of an element that can enter into chemical combination

Question 5

radiation

Answer 5

the emission and transmission of energy through space in the form of waves

Question 6

electrons

Answer 6

negatively charged particles

Question 7

radioactivity

Answer 7

spontaneous emission of particles and/or radiation

any element that spontaneously emits radiation is said to be radioactive

Question 8

alpha rays/particles

Answer 8

positively charged particles; radioactive substances

Question 9

beta rays/particles

Answer 9

negatively charged particles; radioactive substances

Question 10

gamma rays

Answer 10

high-energy rays; radioactive substances

Have no charge and are not affected by an external field

Question 11

nucleus

Answer 11

a dense central core within the atom

Question 12

protons

Answer 12

positively charged particles in the nucleus

Question 13

neutrons

Answer 13

electrically neutral particles having a mass slightly greater than that of protons

Question 14

atomic number

Answer 14

the number of protons in the nucleus of each atom of an element

Question 15

mass number

Answer 15

the total number of neutrons and protons present in the nucleus of an atom of an element

Question 16

isotopes

Answer 16

atoms that have the same atomic number but different mass numbers

Question 17

periodic table

Answer 17

a chart in which elements having similar chemical and physical properties are grouped together

Question 18

periods

Answer 18

horizontal rows of the periodic table

arranged by atomic number

Question 19

groups/families

Answer 19

vertical columns of the periodic table

according to similarities in chemical properties

Question 20

metal

Answer 20

a good conductor of heat and electricity

Question 21

nonmetal

Answer 21

usually a poor conductor of heat and electricity

Question 22

metalloid

Answer 22

has properties that are intermediate between those of metals and nonmetals

Question 23

alkali metals

Answer 23

Group 1A elements: Li, Na, K, Rb, Cs, and Fr

Question 24

alkaline earth metals

Answer 24

Group 2A elements: Be, Mg, Ca, Sr, Ba, Ra

Question 25

halogens

Answer 25

Group 7A elements: F, Cl, Br, I, At

Question 26

noble/rare gases

Answer 26

Group 8A elements: He, Ne, Ar, Kr, Xe, Rn

Question 27

molecule

Answer 27

aggregate of at least two atoms in a definite arrangement held together by chemical forces aka chemical bonds

Question 28

diatomic molecule

Answer 28

contains only two atoms

Question 29

polyatomic molecules

Answer 29

contains more than two atoms

Question 30

ion

Answer 30

an atom or a group of atoms that has a net positive or negative charge

Question 31

cation

Answer 31

an ion with a net positive charge; loses electron(s) tend to be formed by metals

Question 32

anion

Answer 32

an ion whose net charge is negative; gains electron(s) tend to be formed by nonmetals

Question 33

ionic compound

Answer 33

formed from cations and anions

Question 34

monatomic ions

Answer 34

contain only one atom

Question 35

polyatomic ions

Answer 35

ions containing more than one atom hydroxide ion, cyanide ion, ammonium ion

Question 36

chemical formula

Answer 36

express the composition of molecules and ionic compounds in terms of chemical symbols

Question 37

molecular formula

Answer 37

shows the exact number of atoms of each element in the smallest unit of a substance true formulas of molecules

Question 38

allotrope

Answer 38

one of two or more distinct forms of an element oxygen and ozone are allotropes of oxygen

Question 39

structural formula

Answer 39

shows how atoms are bonded to one another in a molecule

Question 40

empirical formula

Answer 40

tells which elements are present and the simplest whole-number ratio of their atoms; not necessarily the actual number of atoms in a given molecule when analyzing unknown compound, first step is to determine compound's empirical formula; can deduce molecular formula with more information later

Question 41

organic compounds

Answer 41

contain carbon, usually in combination with elements such as hydrogen, oxygen, nitrogen, and sulfur

Question 42

inorganic compounds

Answer 42

organized into four categories ionic compounds, molecular compounds, acids and bases, and hydrates compounds that DO NOT contain carbon in combination with hydrogen, oxygen, nitrogen, or sulfur exceptions: carbon monoxide, carbon dioxide, carbon disulfide, compounds containing cyanide group, carbonate groups, bicarbonate groups

Question 43

binary compounds

Answer 43

compounds formed from just two elements name: first element is metal cation followed by nonmetallic anion; anion suffix "-ide"

Question 44

ternary compounds

Answer 44

compounds consisting of three elements name: Roman numeral indicates number of positive charges of transition metal

Question 45

acid

Answer 45

a substance that yields hydrogen ions when dissolved in water

Question 46

oxoacids

Answer 46

acids that contain hydrogen, oxygen and another elements (central element) often two or more oxoacids have the same central atom but a different number of O atoms

Question 47

oxoanions

Answer 47

anions of oxoacids

Question 48

base

Answer 48

a substance that yields hydroxide ions when dissolved in water Ammonia is classified as a common base because the substances yields hydroxide ions when dissolved in water even though it does not contain hydroxide ions in its structure

Question 49

hydrates

Answer 49

compounds that have a specific number of water molecules attached to them