Chapter 4.5: End of Chapter Material

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	Howard University General Chemistry: An Atoms First Approach
Unit 1: Atomic Theory Unit 2: Molecular Structure Unit 3: Stoichiometry Unit 4: Thermochem & Gases Unit 5: States of Matter Unit 6: Kinetics & Equilibria Unit 7: Electro & Thermo Chemistry Unit 8: Materials

Conceptual Problems

Ionic and covalent compounds are held together by electrostatic attractions between oppositely charged particles. Describe the differences in the nature of the attractions in ionic and covalent compounds. Which class of compounds contains pairs of electrons shared between bonded atoms?
Which contains fewer electrons than the neutral atom—the corresponding cation or the anion?
What is the difference between an organic compound and an inorganic compound?
What is the advantage of writing a structural formula as a condensed formula?
The majority of elements that exist as diatomic molecules are found in one group of the periodic table. Identify the group.
Discuss the differences between covalent and ionic compounds with regard to
1. the forces that hold the atoms together.
2. melting points.
3. physical states at room temperature and pressure.
Why do covalent compounds generally tend to have lower melting points than ionic compounds?

Answer

Covalent compounds generally melt at lower temperatures than ionic compounds because the intermolecular interactions that hold the molecules together in a molecular solid are weaker than the electrostatic attractions that hold oppositely charged ions together in an ionic solid.

Numerical Problems

The structural formula for chloroform (CHCl3) was shown in Example 2. Based on this information, draw the structural formula of dichloromethane (CH2Cl2).
What is the total number of electrons present in each ion?
1. F−
2. Rb+
3. Ce3+
4. Zr4+
5. Zn2+
6. Kr2+
7. B3+
What is the total number of electrons present in each ion?
1. Ca2+
2. Se2−
3. In3+
4. Sr2+
5. As3+
6. N3−
7. Tl+
Predict how many electrons are in each ion.
1. an oxygen ion with a −2 charge
2. a beryllium ion with a +2 charge
3. a silver ion with a +1 charge
4. a selenium ion with a +4 charge
5. an iron ion with a +2 charge
6. a chlorine ion with a −1 charge
Predict how many electrons are in each ion.
1. a copper ion with a +2 charge
2. a molybdenum ion with a +4 charge
3. an iodine ion with a −1 charge
4. a gallium ion with a +3 charge
5. an ytterbium ion with a +3 charge
6. a scandium ion with a +3 charge
Predict the charge on the most common monatomic ion formed by each element.
1. chlorine
2. phosphorus
3. scandium
4. magnesium
5. arsenic
6. oxygen
Predict the charge on the most common monatomic ion formed by each element.
1. sodium
2. selenium
3. barium
4. rubidium
5. nitrogen
6. aluminum
For each representation of a monatomic ion, identify the parent atom, write the formula of the ion using an appropriate superscript, and indicate the period and group of the periodic table in which the element is found.
1. 94X2+
2. 11X−
3. 168X2−
For each representation of a monatomic ion, identify the parent atom, write the formula of the ion using an appropriate superscript, and indicate the period and group of the periodic table in which the element is found.
1. 73X+
2. 199X−
3. 2713X3+

Answers

1. 27
2. 38
3. 54
4. 28
5. 67
6. 18
1. Li, Li+, 2nd period, group 1
2. F, F–, 2nd period, group 17
3. Al, Al3+, 3nd period, group 13

Contributors

Anonymous

Modified by Joshua Halpern