Chapter 3

Question 1

Except for Hydrogen, the elements to the left in the periodic table appear first.

Answer 1

KCl PCl₃ Fe₃O₄

Question 2

Hydrogen appears last except when the other element is from Group 16 or 17.

Answer 2

LiH NH₃ C₂H₆ but H₂O₂ H₂S HBr

Question 3

If both elements are from the same group, the one from the lower row appears first

Answer 3

SiC SO₂ BrF₃

Question 4

Structural Formulas

Answer 4

Indicate how the atoms are connected together.

• atoms are held together by bonds, which are represented by lines in structural formulas.

Question 5

Isomers

Answer 5

Isomers are molecules that have the same molecular formula, but different arrangement of atoms.

Ex. CH₃OCH₃ and CH₃CH₂OH

Question 6

Bonds in structural formulas

Answer 6

• each line in a structural formula represents one pair of shared electrons

• single bond
1 line
1 shared pair of electrons

• Double bond
2 lines
2 shared pairs of electrons

•triple bond
3 lines
3 shared pairs of electrons

Question 7

Which two models indicate molecular shape?

Answer 7

• ball-and-stick models

* space-filling models

Question 8

Ball-and-Stick Model

Answer 8

• Balls represent atoms
• sticks represent chemical bonds
• balls are labeled by symbol or color to indicate the element

Question 9

Space-Filling Model

Answer 9

• Atoms are shown as spheres representing electron clouds

* spheres merge to build up the molecules

Question 10

Line Structures

Answer 10

Line structures are compact representations of structural formulas.

• useful for complicated molecules
• large organic molecules
• bio molecules

Question 11

Guidelines for line structures

Answer 11

1. C-H bonds are not shown
2. Show all other bonds as lines
3. Show each single bond as one line, each double bond as two lines and each triple bond as three lines.
4. Label each atom except av and H with its elemental symbol.
5. Label H atoms that are attached to any atom other than C.
6. Do not label C atoms.

Question 12

Naming molecular Binary Compounds

Answer 12

1. The element that appears first keeps its elemental name.
2. The second element begins with a root derived from its elemental name and ends with a suffix -ide.
3. When a formula contains more than one atom of a given element, the name of the element usually contains a prefix that specifies the number of atoms present.

Question 13

Binary Compounds of Hydrogen

Answer 13

• hydrogen compounds do not have systematic names.
• binary hydrogen compounds with elements from groups 1 or 2 are named with hydrogen as the second element.

Ex. LiH is lithium hydride, and CaH₂ is calcium hydride

• hydrogen is listed first in the formulas of the Group 16 and 17 compounds.

Ex. HF is hydrogen fluoride, and HBr is hydrogen bromide

Other unsystematic hydrogen compounds:
Water: H₂O
Hydrogen Peroxide: H₂O₂
Hydrogen Sulfide: H₂S

Question 14

Carbon-Based Compounds

Answer 14

• carbon forms many binary compounds with hydrogen
• three main types of carbon-hydrogen (hydrocarbon) compounds
• alkanes- only single bonds between carbons
• alkenes- at least one double bond between carbons
• alkynes- at least one triple bond between carbons

Question 15

Alkanes

Answer 15

Only single bonds between carbons

Question 16

Alkenes

Answer 16

At least one double bond between carbons

Question 17

Alkynes

Answer 17

At least one triple bond between carbons

Question 18

Prefixes for naming carbon-based compounds

Answer 18

# of Carbons.  Prefix 
1                     meth-
2                     eth-
3                     prop-
4                     but-
5                     pent-
6                     hex-
7                     hept-
8                     oct-

Question 19

Alcohols

Answer 19

Alcohols have at least one hydroxyl (-OH) functional group.

• the systematic name of an alcohol is obtained by adding the suffix -ol to the name of the Alkane with the same carbon framework.

Ex. CH₃OH
•carbon framework of methane
• called methanol

Ex. C₂H₅OH
• carbon framework of ethane
• called ethanol

Question 20

Naming Carbon-Based Compounds with Functional Group Additions

Answer 20

• number the carbons from left to right

* use the number of the carbon to which the addition is attached to identify the location of the addition.

Question 21

Ionic Compounds

Answer 21

Ionic compounds have both a positively-charged ion (cation) and a negatively-charged ion (anion).

•every stable sample of matter must be electrically neutral, so every ionic compound has an equal amount of positive and negative charges.

•Ex. NaCl
Na⁺ and Cl⁻

Question 22

Referring to ionic compounds

Answer 22

• the atoms in ionic compounds are attracted with ionic bonds
• ionic compounds may NOT be referred to as a molecules because the atoms in molecules are connected with covalent bonds
• Ionic Compounds may be referred to as formula units.

Question 23

Chemical formula

Answer 23

Indicate how many atoms of each element there are in a molecule.

Ex. Glucose C₆H₁₂O₆

6 Carbon atoms
12 hydrogen atoms
6 oxygen atoms

Question 24

Common Polyatomic cations

Answer 24

NH₄⁺ Ammonium
H₃O⁺ Hydronium
Hg₂²⁺ Mercury (I)

Question 25

Common polyatomic ions

Diatomic anions

Answer 25

OH⁻ Hydroxide

CN⁻ Cyanide

Question 26

Common polyatomic anions containing carbon

Answer 26

CO₃²⁻ Carbonate
CH₃CO₂⁻ Acetate
C₂O₄²⁻ Oxalate

Question 27

Common Oxoanions

Answer 27

SO₃²⁻
SO₄²⁻
NO₂⁻
NO₃⁻
PO₄³⁻
MnO₄⁻
CrO₄⁻
Cr₂O₇²⁻
ClO⁻
ClO₂⁻
ClO₃⁻
ClO₄⁻

Question 28

A compound is ionic if it contains any one of the following:

Answer 28

1. The ammonium (NH₄⁺) cation
2. Any metal and a polyatomic anion
3. Any Group 1 or 2 metal and a halide (X⁻), oxide (O²⁻), or sulfide (S²⁻) ion

Question 29

Guidelines for ionic formulas

Answer 29

1. The cation/anion ratio must give a net charge of zero.
2. The cation is always listed before the anion.
3. The formula of a polyatomic ion is written as a unit
4. Polyatomic ions are placed in parentheses with a following subscript when the number of polyatomic ions in the formula is larger than 1.

Question 30

Hydrates

Answer 30

Ionic compounds with water molecules incorporated into their solid structures.