Chapter 3

Question 1

Compounds

Answer 1

1. A type of matter composed of two or more different types of atoms
2. Atoms are held together by chemical bonds

Question 2

Ionic Bonds

Answer 2

1. Form when valence electrons are transferred

Question 3

Covalent Bonds

Answer 3

1. Formed when valence electrons are shared

Question 4

Compounds and Valence Electrons

Answer 4

1. Compounds have lower potential energy than the separate atoms that form them
2. Atoms form compounds to attain filled valence energy levels (octet)
3. Noble gas atoms have filled valence energy levels and do not form chemical bonds

Question 5

Ionic Compounds

Answer 5

1. Also called salts
2. Are composed of oppositely charged ions (+) and (-)
3. Simplest ionic compounds contain monatomic ions
   Ex: NaCl

Question 6

Ions

Answer 6

1. A neutral metal atom loses electron(s), forming a positively charged ion, a monatomic cation
2. Neutral nonmetal atoms gain electrons to form negatively charged ions, anions
3. Charge = Number of Protons - Number of Electrons
4. Many Main Group elements have only one ion charge

Question 7

Ionic Compounds

Answer 7

1. Held together by strong attraction of opposite charges
2. Have a net charge equal to zero, determines ratio of cations to anions (formula unit)
3. When a cation and an anion have charges of the same magnitude, the ratio of cation to anion is 1:1
4. Ratio is reflected in subscripts of the compound’s formula unit

Question 8

Ionic Compound Formulas

Answer 8

1. Ionic compounds form in specific ratios to yield neutral compounds
2. Main group elements gain or lose electrons to have the same number of valence electrons as a noble gas (8)
   Ex: calcium and chlorine

Question 9

Electrolytes

Answer 9

1. Ions dissolved in water conduct electricity
2. The most important monatomic electrolytes include:
   - sodium, Na^+
   - potassium, K^+
   - calcium, Ca^2+
   - chloride, Cl^-

Question 10

Transition Metals and Valence Electrons

Answer 10

1. Do not always lose all their valence electrons. Charge is variable
2. Many transition metals can form more than one cation
3. These types of ions use Roman numeral in name to indicate the ion charge
   - Fe^2+ is iron (II)
4. Only elements with variable changes have Roman numerals in name
   - Ag^+ is silver ion

Question 11

Writing the Name from the Formula

Answer 11

1. Name the cation (mostly metals but some exceptions)
2. Name the anion (element – ide)
3. Subscript information is not included
4. Use roman numerals to indicate the charge of ions of metals that can exist in more than one form

Question 12

Polyatomic Ions

Answer 12

1. Derive from molecules, not atoms
2. Contain one or more covalent bonds
3. Contain an unequal number of protons and electrons
4. Each has a unique name, formula and charge

Question 13

Writing Formula Units for Ionic Compounds Containing Polyatomic Ions

Answer 13

1. Same procedure as for monatomic ions
2. Enclose polyatomic ion in parentheses if a subscript is needed. Do not change the name of the ion

Question 14

Covalent Compounds

Answer 14

1. Composed of identical molecules of two or more nonmetal atoms joined by covalent bonds
2. Include a great variety of cellular compounds, such as proteins, carbohydrates, DNA and RNA

Question 15

Diatomic Elements

Answer 15

1. Certain elements exist as molecules
2. Include H2, N2, O2, F2, Cl2, Br2, I2
3. Form a 7 on the periodic table

Question 16

Covalent Bond

Answer 16

1. Two H atoms join to form a molecule of hydrogen (H2)
2. Valence electrons are shared

Question 17

Molecular Formulas

Answer 17

1. It specifies the number of each type of atom in each molecule as subscripts
2. Molecular formula indicate the exact number of atoms needed to build the molecule
3. Differs from the formula unit which indicates the simplest ratio of cations and anions in an array
   3a. ionic compounds use the formula unit

Question 18

Naming Simple Binary Compounds

Answer 18

1. Name the first element, then name the second element changing the ending to -ide
2. Insert prefixes indicating the number of each atom type
3. Mono prefix only used for the second element

Question 19

Mono

Answer 19

One

Question 20

Di

Answer 20

Two

Question 21

Tri

Answer 21

Three

Question 22

Tetra

Answer 22

Four

Question 23

Penta

Answer 23

Five

Question 24

Hexa

Answer 24

Six

Question 25

Hepta

Answer 25

Seven

Question 26

Octa

Answer 26

Eight

Question 27

Nona

Answer 27

Nine

Question 28

Deca

Answer 28

Ten

Question 29

Dot Diagrams

Answer 29

1. Represent the valence electrons with dots around the atom. Valence electrons are responsible for chemical bonding 2. For Main Group, group # = # of valence electrons

Question 30

Nonbonding Pair of Electrons

Answer 30

Dots in a Lewis Structure

Question 31

Bonding Pair of Electrons

Answer 31

Lines in a Lewis Structure

Question 32

Drawing Lewis Structures

Answer 32

1. Sum all the valence electrons. Include the ion charge if an ion 2. Write the element symbols and attach atoms together using single bonds 3. Complete octets using nonbonding electrons 4. Third row and beyond can have expanded octets on the central atom 5. If there are not enough electrons, use double or triple bonds

Question 33

Notable Exceptions for Lewis Structures

Answer 33

1. Hydrogen is a n = 1 element so it is filling only the n = 1 shell. This only requires 2 electrons 2. Nitrogen can have odd number of electrons 3. Be is stable with 4 valence electrons and B with 6 valence electrons

Question 34

Expanded Octets

Answer 34

1. Period 3 elements can have more than 8 electrons in valence energy level = expanded octet

Question 35

Biological Molecules

Answer 35

1. Glucose (carbohydrates) 2. Proteins (amino acids) 3. DNA (nucleotides and phosphates) 4. Heme (hemoglobin)