Chapter 9: Chemical formulas indicate the relative number of atoms of each kind in a chemical compound. ex: C8H18  8 Carbon atoms, 18 Hydrogen atoms Al2(SO4)3  2 Aluminum atoms, 3 Sulfur atoms, and 12 Oxygen atoms Naming Ions ions formed from a single atom are called monatomic ions. Cations: losing electron(s) to form positive ions. K+  potassium cation Mg2+  magnesium cation Anions: gaining electron(s) to form negative ions. F1-  fluoride anion N3-  nitride anion

Zn2+ I1- Zn I 2 Writing Ionic Compounds compounds composed of two different elements are known as binary compounds. the total numbers of positive and negative charges must be equal. Criss-Cross Method Write the formula for the compound zinc iodide. zinc cation iodide anion Zn2+ I1- Zn I 2 Write the formulas for the following binary ionic compounds: Silver chloride Zinc oxide Calcium bromide AgCl ZnO CaBr2

The Stock System most transition metals can form two or more cations with different charges. Roman numerals indicate the charge. ex: iron (II)  Fe2+ iron (III)  Fe3+ Polyatomic Ions Ex: Carbonate anion  (CO3)2- Nitrate anion  (NO3)1- Write the formulas for the following ionic compounds. Sodium carbonate Calcium nitrate Iron(II)sulfate Na2CO3 Ca(NO3)2 FeSO4

Naming Binary Molecular Compounds molecular compounds are made of individual covalently bonded units, or molecules. when naming molecules use prefixes to indicate the number of atoms present. This is a totally different naming system……..DON’T MIX IT UP WITH IONIC COMPOUNDS! # of atoms Prefix 1 mono 6 hexa 2 di 7 hepta 3 tri 8 octa 4 tetra 9 nona 5 penta 10 deca

Ex: Name the following molecules. SO3 ICl3 PBr5 As2O5 Sulfur trioxide Iodine trichloride Phosphorus pentabromide Diarsenic pentoxide

Naming Acids Types Binary Acids: an acid containing H + (halogen) Oxyacids: an acid that contains H + O + (nonmetal) Rules for naming acids Identify the ion within the acid. Change the anion ending to one of the following: Anion ending In acid, replace with: Examples -ide Hydro_____ic acid Hydrochloric Acid, HCl -ite ________ ous acid Nitrous acid, HNO2 -ate _______ic Sulfuric Acid, H2SO4

REMINDER…………. HEED THESE TIPS! “BLAST FROM THE PAST” There are so many formulas, how do I identify them? IONIC COMPOUNDS  Metal + Nonmetal (NAME THE IONS!!!) COVALENT MOLECULES  Nonmetal + Nonmetal (USE PREFIXES!!!) ACIDS  H + (nonmetals) (USE THE CHART!!!) “BLAST FROM THE PAST” Cuprous vs Cupric……..Ferrous vs Ferric “ic” is the higher of the two charges “ous” is the lower of the two charges

Using Chemical Formulas Formula Mass: the sum of the average atomic masses in a molecule or compound. Ex: Write the formula for potassium chlorate and find its formula mass. Potassium chlorate  KClO3 Formula mass = K (39.1amu) + Cl (35.5amu) + 3O (3x16amu) = 122.6 amu Write the formula and determine the formula mass. Magnesium chloride  Calcium nitrate  Barium hydroxide  MgCl2 = 95.2 amu Ca(NO3)2 = 164.1 amu Ba(OH)2 = 171.4 amu