Chapter 2: Atoms, Molecules, and Ions

Question 1

2.1: John Dalton’s Atomic Theory

Answer 1

Question 2

2.2: Cathode Rays

Answer 2

Streams of electrons that are produced when a high voltage is applied to electrodes in an evacuated tube.

Question 3

2.2: Radioactivity

Answer 3

The spontaneous disintegration of an unstable atomic nucleus with accompanying emission of radiation.

Question 4

2.3: Electronic Charge

Answer 4

Question 5

2.3: Atomic Mass Unit (AMU)

Answer 5

Question 6

2.3: Angstrom

Answer 6

Question 7

2.3: Atomic Number

Answer 7

The number of protons in an atom.

Question 8

2.3: Mass Number

Answer 8

The number of protons plus neutrons in the atom.

Question 9

2.3: Isotopes

Answer 9

Atoms with identical atomic numbers but different mass numbers.

Question 10

2.4: Atomic Weight of Isotopes

Answer 10

Question 11

2.5: Periods and Groups of the Periodic Table

Answer 11

Period: The row of elements that lie in a horizontal row in the periodic table.

Group: Elements that are in the same column of the periodic table; elements within the same group or family exhibit similarities in their chemical behavior.

Question 12

2.5: Metals

Answer 12

Elements that are usually solids at room temperature, exhibit high electrical and heat conductivity, and appear lustrous. Most of the elements in the periodic table are metals.

Question 13

2.5: Metalloids

Answer 13

Elements that lie along the diagonal line separating the metals from the nonmetals in the periodic table; the properties of metalloids are intermediat between those of metals and nonmetals.

Question 14

2.5: Nonmetals

Answer 14

Elements in the upper right corner of the periodic table; nonmetals differ from metals in their physical and chemical properties.

Question 15

2.5: Alkali Metals

Answer 15

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

The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1.

Question 16

2.5: Alkaline Earth Metals

Answer 16

Group 2A: Be, Mg, Ca, St, Ba, Ra

They are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure. Orbital contains its full complement of two electrons, which these elements readily lose to form cations with charge +2

Question 17

2.5: Chalcogens

Answer 17

Group 6A: O, S, Se, Te, Po

Question 18

2.5: Halogens

Answer 18

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

When halogens react with metals they produce a wide range of salts. All of the halogens form acids when bonded to hydrogen.

Question 19

2.5: Noble Gases

Answer 19

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

They are all odorless, colorless, monatomic gases with very low chemical reactivity.

Question 20

2.6: Diatomic Molecule

Answer 20

A molecule made up of two atoms.

The halogens (H₂, O₂, N₂, F₂, Cl_2, Br₂, I₂) normally occur as diatomic molecules.

Question 21

2.6: Molecular Compounds

Answer 21

Compounds composed of molecules that contain more than one type of atom.

Question 22

2.6: Molecular and Empirical Formulas

Answer 22

Chemical formulas that indicate the actual numbers of atoms in a molecule are called molecular formulas.

Ethylene: C₂H₄

Chemical formulas that give only the relative number of atoms of each type in a molecule are called empirical formulas.

Ethylene: CH₂

Question 23

2.7: Cation and Anion

Answer 23

An ion with a positive charge is a cation.

Metal atoms tend to lose electrons to form cations.

An ion with a negative charge is an anion.

Nonmetal atoms tend to gain electrons to form anions.

Question 24

2.7: Polyatomic Ion

Answer 24

An electrically charged group of two or more atoms.

Question 25

2.7: Ionic Compound

Answer 25

A compound made up of cations and anions.

The ionic compound sodium chloride (NaCl) is made up of Na⁺ and Cl^-.

Ionic compounds are generally combinations of metals and nonmetals

Question 26

2.8: Names of Cations Formed from Metals

Answer 26

Cations formed from metal atoms have the same name as the metal.

Na⁺ Sodium ion

Zn²⁺ Zinc ion

Al³⁺ Aluminum ion

Question 27

2.8: Names of Cations Formed from Nonmetals

Answer 27

Cations formed from nonmetal atoms have names that end in -ium.

NH₄⁺ Ammonium ion

H₃O⁺ Hydronium ion

Question 28

2.8: Names of Monatomic Anions

Answer 28

The names of monatomic anions are formed by replacing the ending of the name of the element with -ide.

H^- Hydride ion

O^2- Oxide ion

N^3- Nitride ion

Question 29

2.8: Names of Polyatomic Anions

Answer 29

Polyatomic anions containing oxygen have names ending in either -ate or -ite and are called oxyanions. The prefix per- indicates one more O atom than
the oxyanion ending in -ate; hypo- indicates one O atom fewer than the oxyanion ending in -ite.

NO₃^- nitrate ion, NO₂^- nitrite ion

SO₄^2- sulfate ion, SO₃^2-​ sulfite ion

ClO₄^- perchlorate ion, ClO₃^- chlorate ion

ClO₂^- chlorite ion, ClO^- hypochlorite ion

Question 30

2.8: Names of H⁺ Oxyanions

Answer 30

H⁺ oxyanions are named by adding as a prefix the
word hydrogen or dihydrogen, as appropriate.

CO₃^2- carbonate ion, HCO₃^- ​hydrogen carbonate ion

PO₄^3- phosphate ion, H₂PO₄^- ​hydrogen phosphate ion

Question 31

2.8: Names of Ionic Compound

Answer 31

Names of ionic compounds consist of the cation name followed by the anion name.

CaCl₂ calcium chloride

Al(NO₃)₃ aluminum nitrate

Cu(ClO₄)₂ copper (II) perchlorate

Question 32

2.8: Names of Acids with Anions ending in -ide

Answer 32

Acids containing anions whose names end in -ide are named by changing the -ide ending to -ic, adding the prefix hydro- to this anion name, and then following with
the word acid.

Cl^- chloride ►HCl hydrochloric acid

S^2- sulfide ►H₂S hydrosulfuric acid

Answer 33

Acids containing anions whose names end in -ate or -ite are named by changing -ate to -ic and -ite to -ous and then adding the word acid.

ClO₄^- perchlorate ► HClO₄ perchloric acid

ClO₃^- chlorate ► HClO₃ chloric acid

ClO₂^- chlorite ► HClO₂ ​chlorous acid

ClO^- hypochlorite ► HClO hypo​perchlorous acid

Question 34

2.8: Names and Formulas of Binary Molecular Compounds

Answer 34

1. The name of the element farther to the left in the periodic table (closest to the metals) is usually written first. An exception occurs when the compound contains oxygen and chlorine, bromine, or iodine (any halogen except fluorine), in which case oxygen is written last.
2. If both elements are in the same group, the lower one is named first.
3. The name of the second element is given an -ide ending.
4. Greek prefixes are used to indicate the number of atoms of each element. The prefix mono- is never used with the first element. When the prefix ends in a or o and the name of the second element begins with a vowel, the a or o of the prefix is often dropped.

Cl₂O dichlorine monoxide, N₂O₄ dinitrogen tetroxide

NF₃ nitrogen trifluoride,

P₄S₁₀ tetraphosphorus decasulfide

Question 35

2.9: Hydrocarbons

Answer 35

Compounds that contain only carbon and hydrogen.

Question 36

2.9: Alkanes

Answer 36

Each carbon is bonded to four other atoms. Each alkane has a name that ends in -ane.

methane (CH₄), ethane (C₂H₆), propane (C₃H₈)

Question 37

2.9: Alcohol

Answer 37

OH replaces an H atom of an alkane. The name of the alcohol is derived from that of the alkane by adding
an -ol ending.

Question 38

2.9: Isomers

Answer 38

Compounds with the same molecular formula but different arrangements of atoms.