Transcript Document
1
9.3 Naming and Writing Formulas for Molecular Compounds >
Chapter 9 Chemical Names and Formulas 9.1 Naming Ions 9.2 Naming and Writing Formulas for Ionic Compounds
9.3 Naming and Writing Formulas for Molecular Compounds
9.4 Naming and Writing Formulas for Acids and Bases 9.5 The Laws Governing How Compounds Form Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
2
9.3 Naming and Writing Formulas for Molecular Compounds > CHEMISTRY & YOU What numerical prefixes are used in chemistry?
The word
triathlon
contains the prefix
tri
-, indicating the number 3. Prefixes are used in chemistry, too. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
3
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Naming Binary Molecular Compounds
Prefixes used in molecular compounds names.
Prefixes Used in Naming Binary Molecular Compounds Prefix
mono di-
Number
1 2 tri tetra penta hexa hepta 3 4 5 6 7 octa nona deca 8 9 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
4
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds • Recall that binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.
• Binary molecular compounds are also composed of two elements, but both elements are nonmetals and are not ions.
• Binary molecular compounds are composed of molecules, so ionic charges
cannot
be used to write formulas or to name them.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
5
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Naming Binary Molecular Compounds
• Before you apply the steps for naming molecular compounds from their formulas, you must confirm that the compound is a binary molecular
(contains only non-metals)
compound.
• That is done by counting CAPITAL LETTERS and MATCHING up symbols.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
6
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Binary Molecular Compounds
What guidelines are used to write the name and formula of a binary molecular compound?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
7
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
1. Write the names of the elements in the order listed in the formula.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
8
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
1. Write the names of the elements in the order listed in the formula.
2. Use prefixes appropriately to indicate the number of each kind of atom.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
9
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
1. Write the names of the elements in the order listed in the formula.
2. Use prefixes appropriately to indicate the number of each kind of atom.
If just one atom of the first element is in the formula, omit the prefix
mono
- for that element.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
10
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
1. Write the names of the elements in the order listed in the formula.
2. Use prefixes appropriately to indicate the number of each kind of atom.
If just one atom of the first element is in the formula, omit the prefix
mono
- for that element.
3. End the name of the second element with the suffix -ide.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
11
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds • When two nonmetallic elements combine, they often do so in more than one way.
• The elements carbon and oxygen combine to form two gaseous compounds, CO and CO 2 .
• It might seem satisfactory to call both of these compounds carbon oxide but they are VERY different.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
12
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds • CO is a
poisonous gas
that interferes with your blood’s ability to carry oxygen to body cells.
• You
exhale
CO 2 as a product of your body chemistry, and is vital for the production of oxygen gas in green plants.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
13
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Naming Binary Molecular Compounds
• Prefixes in the names of binary molecular compounds tell how many atoms of an element are present in each molecule of the compound.
• The prefix
mono
- would be used for the single oxygen atom in CO.
• The prefix
di-
would be used for the two oxygen atoms in CO 2 . Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
How does phosphorus trifluoride differ from phosphorus pentafluoride?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
How does phosphorus trifluoride differ from phosphorus pentafluoride?
Phosphorus trifluoride is a binary molecular compound that has 1 phosphorus and 3 fluoride atoms, while phosphorus pentafluoride contains 1 phosphorus and 5 fluoride atoms.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
16
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Naming Binary Molecular Compounds
• Following the guidelines, CO is named carbon
mon
oxide and CO 2 is named carbon
di
oxide.
• Cℓ 2 O 8 consists of two chlorine atoms and eight oxygen atoms.
• The name is therefore
di
chlorine
oct
oxide.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
17
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem
Naming Binary Molecular Compounds
Name the following binary molecular compounds.
a. N 2 Br b.
HCℓ 3 c. C 4 O 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample
Problem
1 Analyze Identify the relevant concepts.
Confirm that the compound is a binary molecular compound —a compound composed of two nonmetals. To name the compound, name the elements in the order written in the formula. Use prefixes as necessary to indicate the number of each kind of atom. Use the suffix -
ide
name of the second element.
on the Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample
Problem
2 Solve Apply the concepts to this problem.
Identify the elements in the compound and the number of atoms of each element in a molecule of the compound.
a. N 2 Br is composed of two nonmetals, nitrogen and bromine .
b. H Cℓ 3 is composed of two nonmetals, hydrogen and chlorine .
c. C 4 O 4 is composed of two nonmetals, carbon and oxygen .
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
20
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem
2 Solve Apply the concepts to this problem.
Write the names of the elements in the order they are written in the formula. Include prefixes to show how many atoms of each element. Use the suffix
-ide
with the name of the second element.
a. Each molecule of N 2 Br has: 2 nitrogen atoms; 1 bromine atom.
N 2 Br is dinitrogen monobromide.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem 21
2 Solve Apply the concepts to this problem.
Write the names of the elements in the order they are written in the formula. Include prefixes to show how many atoms of each element. Use the suffix -
ide
with the name of the second element.
b. Each molecule of H Cℓ 3 1 hydrogen atom; 3 chlorine atoms.
has: The prefix
mono-
is not used with the first element .
H Cℓ 3 is hydrogen trichloride.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
22
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem
2 Solve Apply the concepts to this problem.
Write the names of the elements in the order they are written in the formula. Include prefixes to show how many atoms of each element. Use the suffix
-ide
with the name of the second element.
a. Each molecule of C 4 O 4 4 carbon atoms; 4 oxygen atom.
has: C 4 O 4 is tetracarbon tetraoxide.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
23
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Writing Formulas for Binary Molecular Compounds To write the formula of a binary molecular compound, first use the prefixes in the name to tell you the subscript of each element in the formula. Then, write the correct symbols for the two elements with the appropriate subscripts.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
24
9.3 Naming and Writing Formulas for Molecular Compounds >
Binary Molecular Compounds
Writing Formulas for Binary Molecular Compounds
• T
etraphosphorus trisulfide,
which is used in some matches, has the prefixes
tetra-
and
tri-
, so the subscripts of phosphorus and sulfur must be 4 and 3, respectively.
• Thus, the formula for tetraphosphorus trisulfide is P 4 S 3 .
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem 25
Writing Formulas for Binary Molecular Compounds
Write formulas for the following binary molecular compounds.
a. nitrogen octafluoride b. disulfur dichloride c. decaboron nonaiodide Note: The number 1 is never used as a subscript in a formula.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample
Problem
1 Analyze Identify the relevant concepts.
The prefixes in the name indicate the subscript of each element in the formula. Write the symbols for the two elements with the appropriate subscripts.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Sample
Problem
2 Solve Apply the concepts to this problem.
Use the prefixes to determine how many atoms of each element are in the compound.
a. Each molecule of nitrogen octafluoride has: 1 nitrogen atom; 8 fluorine atoms.
b. Each molecule of disulfur dichloride has: 2 sulfur atoms; 2 chlorine atoms.
c. Each molecule of decaboron nonaiodide has: 10 boron atoms; 9 iodine atoms.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
28
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem
2 Solve Apply the concepts to this problem.
Construct the formula using the correct symbols and subscripts. a. 1 nitrogen atom; 8 fluorine atoms NF 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
29
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem
2 Solve Apply the concepts to this problem.
Construct the formula using the correct symbols and subscripts. b. 2 sulfur atoms; 2 chlorine atoms S 2 Cℓ 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
30
9.3 Naming and Writing Formulas for Molecular Compounds > Sample
Problem
2 Solve Apply the concepts to this problem.
Construct the formula using the correct symbols and subscripts. c. 10 boron atom; 9 iodine atoms B 10 I 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Compare and Contrast binary molecular compounds from binary ionic compounds?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Compare and Contrast binary molecular compounds from binary ionic compounds?
Binary molecular compounds are composed of two elements, which are nonmetals and are not ions. Binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
33
9.3 Naming and Writing Formulas for Molecular Compounds >
Key Concepts To name a binary molecular compound, write the names of the elements in the order listed in the formula. Use prefixes to indicate the number of each atom. End the name of the second element with -
ide
.
To write the formula of a binary molecular compound, use the prefixes to determine the subscript of each element. Write the symbols for the elements with the subscripts.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
9.3 Naming and Writing Formulas for Molecular Compounds >
END OF 9.3
34 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.