Ionic Compounds
This is Important! On the Periodic Table remember where to: find the metals and the nonmetals
If You Don t Remember How to Tell Metals From Nonmetals, Nothing in This Chapter Will Make Sense!
Ionic Compounds There are two types of ionic compounds 1. Binary ionic compounds and 2. Ionic compounds that contain polyatomic ions.
Binary Ionic Compounds
Type 1: Binary Ionic Compounds 1. Binary means 2 (as in bicycle 2 wheels ) A binary ionic compound has only 2 elements: (example: BaCl 2 ) 1.The first element is always a metal! 2.The second element is always a nonmetal!
Type 1: Binary Ionic Compounds 2 elements means just that 2 elements! There can be more than one ion of an element! Example: AlF 3 AlF 3 contains only 2 elements: Al & F. AlF 3 has 1 Al +3 ion, and 3 F -1 ions. {metal (+) & nonmetal (-)} The subscript tells you how many ions are in the compound (a 1 is understood and not written)
Naming Binary Ionic Compounds
Naming Binary Ionic Compounds To name a binary ionic compound 1. Write the name of the metal ion (+) (this is just the name of the metal) 2. Write the name of the nonmetal ion (-) (the nonmetal ion has the same root as the nonmetal, but with an -ide suffix). Examples: chlorine becomes chloride oxygen becomes oxide nitrogen becomes nitride
Naming Binary Ionic Compounds That s It!! Just write the metal ion name first, then the nonmetal ion name second! (remember the ide nonmetal ending) Practice: (name these) K 2 S MgO Sr 3 As 2 potassium sulfide magnesium oxide strontium arsenide
Writing the Formula of a Binary Ionic Compound
Writing Binary Ionic Compounds Remember, metals are always (+) because they lose electrons, and Nonmetals are always (-) because they gain electrons!! In any ionic compound, the total (+) must EQUAL the total (-)!!
Writing Binary Ionic Compounds To write a binary ionic compound formula you must know the charge of the metal ion and the nonmetal ion! There are two ways to know these Memorize them, or Look at the periodic table! Guess which is easier?!
Writing Binary Ionic Compounds You Guessed it! The representative elements are easy! +1 +2 0 Each family has +3 IVA -3-2 -1 its own charge! Noble gas wannabe s, remember? In Family IVA (14), only Sn and Pb form ions
Writing Binary Ionic Compounds The transition metals do not follow any simple rules. (Many can even have two possible charges!) Some must be memorized, but, there IS an easy system for the others The Roman Numeral after the name gives you the (+) charge! Examples: copper(i) = Cu +1 iron(iii) = Fe +3 lead(iv) = Pb +4
Writing Binary Ionic Compounds IONIC COMPOUNDS ARE NEUTRAL!! Be sure the (+) charges = the (-) charges! Example: aluminum fluoride aluminum ions are Al +3 fluoride ions are F -1 Al +3 F -1 AlF 3 (Al +3 + F -1 + F -1 + F -1 ) The compound has NO charge! Adds up to zero!
Writing Binary Ionic Compounds Practice: write the formula for: calcium fluoride +1 +2 CaF 2 +3-3 -2-1 aluminum oxide Al 2 O 3 lithium phosphide Li 3 P copper(ii) chloride Cu +2 and Cl -1 CuCl 2
Writing Binary Ionic Compounds Ionic formulas are formula units of ionic compounds ionic compounds can t form molecules! Remember to reduce any ionic formula to a lowest ratio Example: barium oxide Ba +2 O -2 Ba 2 O 2? Reduce to BaO Special Note: be SURE to write element symbols clearly! Lower and upper case letters must be obvious!
Compounds Containing Polyatomic Ions
Type 2: Ionic Compounds Containing Polyatomic Ions Polyatomic ions are GROUPS of atoms with a charge! (most will have a negative (-) charge, just like a non-metal ion) You will be given a list of these to use
poly means many, so polyatomic means many atoms! (These are ions made of groups of atoms)! An example: the polyatomic ion, nitrate Polyatomic Ions O N O O This group of atoms carries a charge of (-1). -1 Nitrate s formula is: NO 3-1 contains 1 nitrogen and 3 oxygen atoms!
Naming Compounds with Polyatomic ions
Naming Ionic Compounds With Polyatomic Ions To name an ionic compound with polyatomic ions is really EASY 1.Write the name of the positive ion (+) (usually the name of the metal) 2.Write the name of the negative ion (-) (usually the polyatomic ion) That s IT!! Example: Mg(NO 3 ) 2 magnesium nitrate
Writing the Formula of a Compound That Contains Polyatomic Ions
Formulae with Polyatomic ions To write a formula using polyatomic ions, you must know the formula and charge of the metal ion and the polyatomic ion. The metal ions you know (periodic table) you will have a list of polyatomic ions with their formulas and charges.
Formulae with Polyatomic ions In ALL ionic compounds, the total (+) must be equal to the total (-)!! Just look at the charges, and make sure they add up to zero. Example: sodium carbonate sodium = Na +1 carbonate = CO 3-2 Na +1 CO 3-2 Na +1 + Na +1 + CO -2 3 Na 2 CO 3 Adds up to zero!
Formulae with Polyatomic ions What if more than one polyatomic ion is needed? Wrap the polyatomic ion in parenthesis! Example: aluminum sulfate aluminum ions are Al +3 sulfate ions are SO 4-2 Al +3 SO 4-2 (Al +3 + Al +3 + SO 4-2 + SO 4-2 + SO 4-2 ) Al 2 (SO 4 ) 3 Adds up to zero! 2 Al +3 3 SO 4-2
A Final Note Some ionic compounds collect water from the moisture in the air. They trap this collected water in their crystals. When they have trapped this water, they are called hydrates. Their formula includes water, written after a raised dot: MgSO 4 5H 2 0 (magnesium sulfate * pentahydrate) *(Prefixes in your notes)