chemistry

1. chemistry Section 9.3-1 Naming Molecular Compounds

2. Naming and Writing Formulas for Molecular Compounds 9.3-1 • One milligram of gold (0.01 g) 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 tells you its composition.

3. 9.3-1 Naming Binary Molecular Compounds • Naming Binary Molecular Compounds • What does a prefix in the name of a binary molecular compound tell you about the compound’s composition?

4. 9.3-1 Naming Binary Molecular Compounds • A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule of the compound. • The table below lists the prefixes used for each amount of atoms in the compound.

5. 9.3-1 Naming Binary Molecular Compounds • Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO2), but these two invisible gases are very different. • Both are produced by the automobile. One is harmful, and the other one is not. Do you know which one is which?

6. 9.3-1 Naming Binary Molecular Compounds • Sitting in a room with small amounts of CO2 in the air would not present any problems. You do it every day. However, if the same amount of CO were in the room, you could die of poisoning (asphyxiation). A naming system that distinguishes between these two compounds is needed.

7. 9.3-1 Naming Binary Molecular Compounds • Some guidelines for naming binary molecular compounds: • Name the elements in the order listed in the molecular formula. • Use prefixes to indicate the number of each kind of atom. • On the 1st element, only use the prefix if there is more than one. • On the 2nd element, alwaysuse the prefix.

8. 9.3-1 Naming Binary Molecular Compounds Again, A Recap of the Rules: • Do not use (omit) the prefix mono- when the molecular compound contains only one atom of the 1st element in the name. All the rest (2 or more) use a prefix. • The suffix (ending) of the name of the second element always “ide”. • Prefixes are alwaysused with the 2nd element of the compound.

9. 9.3-1 Naming Binary Molecular Compounds • Now, for some Practice. • SiO2 • N2O3 • H2O • NO silicon dioxide (sand) trioxide dinitrogen dihydrogen monoxide (water) monoxide nitrogen

10. 9.3-1 Writing Formulas for BinaryMolecular Compounds • Writing Formulas for Binary Molecular Compounds • How do you write the formula for a binary molecular compound from the compound name? • (You just do the opposite of what you just did ! ! !)

11. 9.3-1 Writing Formulas for BinaryMolecular Compounds • Use the prefixes in the name to tell you the subscript (amount) of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts.

12. 9.3-1 Writing Formulas for BinaryMolecular 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.

13. 9.3-1 Section Quiz. • 1. Which of the following compounds is named INCORRECTLY? • CS2, carbon disulfide • BCl3, boron trichloride • IF7, iodine heptafluoride • PCl5, phosphorus hexachloride

14. 9.3-1 Section Quiz. • 2. Which of the following molecular compounds is named INCORRECTLY? • SbCl3, antimony trichloride • C2O5, dicarbon pentoxide • CF4, carbon tetrafluoride • H3As, hydrogen arsenide

15. 9.3-1 Section Quiz. • 3. The correct formula for tetraphosphorus trisulfide is • P3S4 • S3P4 • P4S3 • S4P3

16. The End