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!

There are two types of ionic compounds… Binary ionic compounds and… 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: BaCl2) The first element is always a metal! 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: AlF3 AlF3 contains only 2 elements: Al & F. AlF3 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… Write the name of the metal ion (+)… (this is just the name of the metal) 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)… K2S MgO Sr3As2 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 Each family has its own charge! +2 +3 -3 -2 -1 IVA 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 AlF3 (Al+3 + F-1 + F-1 + F-1) Adds up to zero! The compound has NO charge!

Writing Binary Ionic Compounds Practice: write the formula for: +1 calcium fluoride +2 CaF2 +3 -3 -2 -1 aluminum oxide Al2O3 lithium phosphide copper(II) chloride Li3P CuCl2 Cu+2 and Cl-1

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 Ba2O2? Reduce to “BaO” Special Note: be SURE to write element symbols clearly! Lower and upper case letters must be obvious!

Compounds Containing Polyatomic Ions

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”! Polyatomic Ions “poly” means “many”, so… “polyatomic” means “many atoms”! (These are ions made of groups of atoms)! -1 Nitrate’s formula is: NO3-1 An example: the polyatomic ion, “nitrate”… O N O O …contains 1 nitrogen and 3 oxygen atoms! This group of atoms carries a charge of (-1).

Naming Compounds with Polyatomic ions

Naming Ionic Compounds With Polyatomic Ions To name an ionic compound with polyatomic ions is really EASY… Write the name of the positive ion (+)… (usually the name of the metal) Write the name of the negative ion (-)… (usually the polyatomic ion) That’s IT!! Example: Mg(NO3)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” = CO3-2 Na+1 CO3-2 “Na2CO3” Na+1 + Na+1 + CO3-2 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 SO4-2 Al+3 SO4-2 Al2(SO4)3 2 Al+3 3 SO4-2 (Al+3 + Al+3 + SO4-2 + SO4-2 + SO4-2) Adds up to zero!

*(Prefixes in your notes) 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: MgSO4 · 5H20 *(Prefixes in your notes) * (magnesium sulfate pentahydrate)