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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)
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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? • 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:
Examples • H2O • N2O4 • P4S3 • SiI4 • PCl3 • P4O10
Remember the Name • Chemistry Remix • Follow along with the lyrics on the back of your HRL