Slide 1 of 15 chemistry

© Copyright Pearson Prentice Hall Slide 2 of 15 Naming and Writing Formulas for Molecular Compounds One milligram of gold is worth only about one cent, but one kilogram of gold is worth approximately $12,500. The correct prefix ( milli- or kilo-) makes quite a difference! Prefixes are important in chemistry, too. The prefixes in the name of a binary molecular compound tell you its composition. Objectives: Interpret the prefixes in the names of molecular compounds in terms of their chemical formulas Apply the rules for naming and writing formulas for binary molecular compounds 9.3

© Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Slide 3 of 15 Naming Binary Molecular Compounds What does a prefix in the name of a binary molecular compound tell you about the compound’s composition? 9.3

Slide 4 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO 2 ), but these two invisible gases are very different. 9.3 Naming Binary Molecular Compounds

Slide 5 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Sitting in a room with small amounts of CO 2 in the air would not present any problems. If the same amount of CO were in the room, you could die of asphyxiation. A naming system that distinguishes between these two compounds is needed. 9.3 Naming Binary Molecular Compounds

Slide 6 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule 9.3 Naming Binary Molecular Compounds

Slide 7 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > To name binary molecular compounds: 1. Name the elements in the order listed in the formula. 2. Use prefixes to indicate the number of each kind of atom. 3. Omit the prefix mono- when the formula contains only one atom of the first element in the name. 4.The suffix of the name of the second element is -ide. 9.3 Naming Binary Molecular Compounds

Slide 8 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Molecular compounds Example: Name the following binary molecular compounds: 1.P 2 O 3 2.CCl 4 3.N 2 O

Slide 9 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Writing Formulas for Binary Molecular Compounds Writing Formulas for Binary Molecular Compounds How do you write the formula for a binary molecular compound? 1.Write the symbol of each anion 2.Use the prefix in front of each name to assign a subscript to that particular cation 3.DO NOT CRISSCROSS! 9.3

Slide 10 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Silicon carbide is a hard material like diamond. The name silicon carbide has no prefixes, so the subscripts of silicon and carbon must be one. Thus, the formula for silicon carbide is SiC. 9.3 Writing Formulas for Binary Molecular Compounds

Slide 11 of 15 © Copyright Pearson Prentice Hall Naming and Writing Formulas for Molecular Compounds > Molecular compounds Example: Write the formula for each of the following: 1.Sulfur trioxide 2.Silicon tetrachloride 3.Carbon monoxide

© Copyright Pearson Prentice Hall Section Quiz -or- Slide 12 of 15 Continue to: Launch: Assess students’ understanding of the concepts in Section Section Quiz.

© Copyright Pearson Prentice Hall Slide 13 of Section Quiz. 1.Which of the following compounds is named INCORRECTLY? a.CS 2, carbon disulfide b.BCl 3, boron trichloride c.IF 7, iodine heptafluoride d.PCl 5, phosphorus hexachloride

© Copyright Pearson Prentice Hall Slide 14 of 15 2.Which of the following molecular compounds is named INCORRECTLY? a.SbCl 3, antimony trichloride b.C 2 O 5, dicarbon pentoxide c.CF 4, carbon tetrafluoride d.H 3 As, hydrogen arsenide 9.3 Section Quiz.

© Copyright Pearson Prentice Hall Slide 15 of 15 3.The correct formula for tetraphosphorus trisulfide is a.P 3 S 4 b.S 3 P 4 c.P 4 S 3 d.S 4 P Section Quiz.

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