Chapter 9 Chemical Names and Formulas Mr. Roberts Chemistry Level 2

Section 1 – Naming Cations Group A Elements Just write name of metal and add “ion” to ending Example: Na+1 sodium ion Al+3 aluminum ion

Naming Cations Group B Elements (transition metals) Ionic charge will change so write Roman Numerals in parenthesis after name of metal to indicate charge. (Stock System) Table 9.2 page 255

Naming Cations Some post transition element also have charges that will change. Ex: Tin and Lead Sn+2 Sn+4 Pb+2 Pb+4 Some transition metals only have one ionic charge. Therefore you don’t use roman numerals. Silver Ag+1 Cadmium Cd+2 Zinc Zn+2

Naming Anions Always have the same charge! Change suffix with - ide Ex: F-1 Fluoride ion O-2 Oxide ion

Polyatomic Ions Group of atoms that stay together and have an overall charge Usually end with –ate or –ite (one less oxygen) Ex: (SO3)-2 Sulfite (SO4)-2 Sulfate (NH4)+1 ammonium

Section 2 – Writing/Naming Ionic Compounds Finding the formulas for ionic compounds. Criss-Cross Method Remember…ionic compounds must be expressed in the lowest whole number ratio. Lose sign value

Naming Ionic Compounds Binary Ionic Compounds (2 ions) Use rules for naming ions Ex: Na+1Cl-1 {sodium ion and chloride ion} NaCl Sodium Chloride

Naming Ionic Compounds (continued) Naming Ternary Ionic Compounds (involving a polyatomic ion group) Name it as it appears Ex: CaCO3 calcium carbonate Mg3(PO4)2 magnesium phosphate CaSO4 calcium sulfate If ammonium or any other polyatomic cation is reacting with a monatomic anion use binary ionic rules

Naming Group B Ionic Compounds Rules for naming binary and ternary ionic compounds apply Include a roman numeral in parenthesis to indicate the ionic charge. Use the reverse of the criss cross method to determine the charge. Ex:

Section 3 – Molecular Compounds Naming Binary molecular compounds (2 nonmetals) Name the elements in order they appear. Drop ending of second element and replace with suffix “ide”. Use prefixes to indicate # of atoms present Table 9.4 page 269

Binary Molecular Compounds Mono = 1 Di = 2 Tri = 3 Tetra = 4 Penta = 5 Hexa = 6 Hepta = 7 Octa = 8 Nona = 9 Deca = 10 Examples: N2O dinitrogen monoxide CO2 carbon dioxide CO carbon monoxide SF6 sulfur hexafluoride

9.4 Naming and Writing Acids Acid: a compound contain H+ ions. Anion Ending Acid Name with Suffix Acid Ending Example - ide hydro________ic acid HCl – hydrochloric - ite ____________ous H2SO3 – sulfurous - ate _____________ic H2SO4 – sulfuric

Examples HF HClO2 HClO3 Hydrofluoric Acid Chlorous Acid Chloric Acid

Naming and Writing Bases Base: a compound containing OH-1 Named in the same way as other ionic compounds Example: NaOH sodium hydroxide

Section 9.5 – The Laws Governing Formulas and Names We are able to name compounds and write their formulas because they form from elements in predictable ways

1. The Law of Definite Proportions In samples of any chemical compound, the masses of the elements are always in the same proportions.

2. The Law of Multiple Proportions Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers. John Dalton