Compound Names and Formulas Section 4.3

Naming Compounds Each compound has a unique name Relatively easy rules for naming ionic and covalent compounds

Naming Ionic Compounds Name of cation stays the same Lithium atom  lithium (ion) Magnesium atom  magnesium (ion) Name of anion turns into an “ide” Chlorine atom  chloride (ion) Iodine atom  iodide (ion) Name = cation + anion Lithium + Chlorine  Lithium Chloride

More examples of ionic compounds Barium Chloride Magnesium Bromide Sodium Sulfide Cesium Nitride Rubidium Oxide Lithium Fluoride Potassium Chloride

Predicting the number of cations & anions in an ionic compound Example: Magnesium Fluoride Magnesium cation has a +2 charge Fluoride has a -1 charge Mg2+F-1 Rule: Erase charges, replace superscripts with subscripts and switch the numbers between the ions

Example: 2+ 2 1- 1 Mg F

Why? -1 -1 2+ Magnesium cation: +2 charge Fluoride anion: -1 charge It takes TWO fluoride ions to cancel out the charge of the magnesium cation. -1 -1 2+

Example #2: -2 -2 -2 3+ 3+ 3 2- 2 Al O 3+ It takes 2 aluminum ions and 3 oxide ions to cancel out the charges!

Example #3: -2 2+ 2+ 2 2- 2 Ca S Since the charges are equal, it only takes one of each to make the compound neutral!

Ionic bonds with transition metals Many transition metals can take on more than one charge as an ion: Cu+, Cu2+ Fe2+, Fe3+ If Cu+ bonds to F-, you get CuF If Cu2+ bonds to F-, you get CuF2 Both cannot be called “Copper Fluoride” What can we do?

The answer! Designate the charge of the cation in the name by using Roman numerals! CuF contains a copper cation of charge +1 We call this Copper (I) Fluoride CuF2 contains a copper cation of charge +2 We call this Copper (II) Fluoride Rule: When working with transition metals, put the charge of the cation in parentheses using Roman numerals!

Naming Covalent Compounds Let’s look at one we already know: Carbon Dioxide (CO2) The first element is named regularly (carbon) The second element gets an “-ide” The number of each element is represented by a prefix. Rule: If there is only one atom of the first element, it does not get a prefix. Otherwise, the first and second elements get prefixes according to the following table:

Table of prefixes Number of Atoms Prefix 1 Mono- 2 Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa- 7 Hepta- 8 Octa- 9 Nona- 10 Deca-

Examples H2O N2O4 P4S3 SiI4 PCl3 P4O10 Number of Atoms Prefix 1 Mono- Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa- 7 Hepta- 8 Octa- 9 Nona- 10 Deca- H2O N2O4 P4S3 SiI4 PCl3 P4O10

Remember the Name Chemistry Remix Follow along with the lyrics on the back of your HRL