Chemical Formulas and Equations Chapter 9 – 2 Part 1

Chemical Formulas A chemical formula is a shorthand way to use chemical symbols and numbers to represent a substance. A subscript is a number written below and to the right. It tells how many atoms are in this molecule. If there is no subscript, then there is just one atom. C6H12O6 Glucose

Some Basic Rules When you have two elements, you have two words in the name The first word is the first element. The second word is the second element.

Continued The second word also ends in “IDE”. Like oxygen becomes oxide.

Writing Formulas for COVALENT COMPOUNDS Covalent compounds are often composed of nonmetals. The names of many covalent compounds use prefixes. Example: Carbon Dioxide & Dinitrogen monoxide CO2 N2O

Here are the first ten prefixes: Mono- 1 Hexa- 6 Di- 2 Hepta- 7 Tri- 3 Octa- 8 Tetra- 4 Nona- 9 Penta- 5 Deca- 10 Prefixes Used in Chemical Names

Writing Formulas Covalent Compounds Use the name of compound to write its formula Ex: Carbon Dioxide No prefix on first atom indicates 1 atom The prefix di indicates 2 oxygen atoms= CO2 Prefixes always used on second atom C0 = carbon monoxide What is the formula for dinitrogen trioxide? ––> N2O3

More Practice 1. Dihydrogen monoxide 2. Silicon dioxide 3. Carbon monoxide 4. Hydrogen bromide 1. H2O 2. SiO2 3. CO 4. HBr

LET’S TRY IT! SiF4 Silicon tetrafluoride SF6 Sulfur hexafluoride N2O5 Dinitrogen pentaoxide