Chapter 2 Atoms, Molecules, and Ions

Chemistry, The Central Science, 10th edition

Theodore L. Brown; H. Eugene LeMay, Jr.;and Bruce E. Bursten

Chapter 2Atoms, Molecules,

and Ions

Troy WoodUniversity of BuffaloBuffalo, NY 2006, Prentice Hall

How many neutrons are there in an atom of 14C?

1. 62. 83. 124. 14

Correct Answer:

Atomic numberMass number 14

6 CThe difference between the mass number and the atomic number is the number of neutrons (14 6) = 8.

1.6

2.8

3.12

4.14

An isotope of Cr3+ ion containing 24 protons and 27 neutrons would contain ___ electrons.

1. 21

2. 24

3. 27

4. 3

Correct Answer:

The +3 charge indicates there are 3 more protons than electrons:

24 3 = 21

1. 21

2. 24

3. 27

4. 3

A hypothetical element has two isotopes. One of the isotopes has an abundance of 75.0% and a relative mass of 12.0 amu, while the other has an abundance of 25.0% and a relative mass of 14.0 amu. The atomic mass

of this hypothetical element is

1. 12.5 amu.2. 13.0 amu.

3.13.5 amu.4.13.8 amu.

Correct Answer:

Atomic mass = (0.750)(12.0 amu) + (0.250)(14.0 amu)

Atomic mass = 9.0 amu + 3.5 amu = 12.5 amu

1. 12.5 amu.2. 13.0 amu.

3.13.5 amu.4.13.8 amu.

Chlorine has two isotopes, 35Cl (75.78% abundant) and 37Cl (24.22% abundant). How many different molar masses are possible for a Cl2 molecule?

1. 22. 33. 44. 5

Correct Answer:

35Cl2 = 70 amu35Cl37Cl = 72 amu37Cl2 = 74 amu

1. 22. 33. 44. 5

Which of the following species has the greatest number of electrons?

1. Cl

2. Ca2+

3. P3

4. K5. Ar

Correct Answer:

K has 19 electrons; all the other species listed have only 18 electrons.

1. Cl

2. Ca2+

3. P3

4. K5. Ar

The compound, CuSO4, is called

1. Calcium sulfide2. Carbon sulfide3. Calcium sulfite4. Calcium sulfate5. Copper sulfate

Correct Answer:

The compound is ionic, derived from the copper(II) cation (Cu2+) and the sulfate anion (SO4

2).

1. Calcium sulfide2. Carbon sulfide3. Calcium sulfite4. Calcium sulfate5. Copper sulfate

The correct name for the compound, MgC2 is

1. Carbon magneside2. Magnesium carbide3. Magnesium carbonate4. Manganese dicarbide5. Magnesium dicarbide

Correct Answer:

In this unusual ionic compound, the cation is magnesium cation (Mg2+) and the anion is carbide or acetylide (C2

2).

1. Carbon magneside2. Magnesium carbide3. Magnesium carbonate4. Manganese dicarbide5. Magnesium dicarbide

The simplest chemical formula for the binary ionic compound CaxNy is

1. Ca2N2. Ca2N3

3. Ca3N2

4. Ca3N

Correct Answer:

Ca loses two electrons to become Ca2+, while N gains three electrons to become N3

. To be neutral, positive charges and negative charges have to balance.

1. Ca2N2. Ca2N3

3. Ca3N2

4. Ca3N

The ion Cr2O72 is known as:

1. Chromos2. Chromite3. Chromate4. Dichromate5. Bichromite

Correct Answer:

Dichromate solutions are a deep orange color.

1. Chromos2. Chromite3. Chromate4. Dichromate5. Bichromite

The acid HClO3 is known as:

ClO

O

HO1. Perchloric acid2. Chloric acid3. Chlorous acid4. Hypochlorous acid5. Hydrochloric acid

Correct Answer:

ClO

O

HO1. Perchloric acid2. Chloric acid3. Chlorous acid4. Hypochlorous acid5. Hydrochloric acid

The molecular compound N2O4 is named:

1. Nitrogen oxide2. Oxygen nitride3. Dinitrogen quartoxide4. Dinitrogen tetroxide5. Nitrous oxide

Correct Answer:

Remember: the vowel “A” on the prefix tetra- is dropped because oxide starts with the vowel “O.”

1. Nitrogen oxide2. Oxygen nitride3. Dinitrogen quartoxide4. Dinitrogen tetroxide5. Nitrous oxide