Names and Formulas for Ionic Compounds

Formula Unit Review In ionic compounds, we must balance charges to form a neutral compound To do that, we “crisscross the charges” similar to find the least common denominator in a fraction Always write the cation first (metal) followed by the anion (nonmetal) Ca and N, what will the formula be?

Practice Al and S Mg and O Na and N

Formula Unit with Polyatomic ions Sometimes you will need to use more than one polyatomic ion to balance a charge. If so, you need to put it in parenthesis (like a package) and use a subscript for the multiple number Ex: Mg2+ and PO43− These charges do not balance so we must crisscross them Mg3(PO4)2 Mg3 (PO4)2

Naming Ca”t”ions Monatomic cation name stays the same Sodium, Na goes to sodium ion, Na+ Calcium, Ca goes to calcium ion, Ca 2+ Polyatomic cation - look up in chart NH4+ ammonium What is a cation?

Naming Anions The name changes in a monatomic anion The ending for a monatomic anion is ______ide (like a bride changes her last name) chlorine, Cl goes to chloride ion, Cl- Fluorine, F goes to fluoride ion, F- Polyatomic anion look up in chart OH- hydroxide SO42- sulfate

Naming ionic compounds Name the cation first and then the anion second (+ then -) Example: CsF Monatomic cations use the element name Cs+ = cesium ion Monatomic anions – change the ending to ide F - = fluoride ion cesium fluoride

Practice Name the following compounds NaBr sodium bromide CaCl2 KOH calcium chloride potassium hydroxide

Will these form an Ionic Compound? If so what will the formula name be? Mg Al Al S Mg O Na N C S No two metals Yes aluminum sulfide Yes magnesium oxide Yes sodium nitride No two non-metals

Transition Metal Ions Transitions metals will form cations Some transition metals only have one ionic charge Silver (Ag+), Cadmium (Cd2+), Zinc (Zn2+) Some transition metals can take on more than one charge. Copper (Cu+, Cu2+) Charge is determined from the number of electrons lost Transition metals form compounds the same way all cations do, which enables us to find the formula units in a similar fashion.

Naming Transition Metal Ions If a transition metal has more than one charge, the charge is written as a Roman numeral in parenthesis Some metals need a middle name Fe (iron) has more than one charge: 2+ and 3+ Fe2+ iron(II) Fe3+ iron(III) If the transition metal only has one charge, no Roman numeral is needed

Naming Ionic Compounds with Transition Metals Given: Fe2O3 First find the charges of the ions Then name the cation followed by the anion Iron(III)oxide Try this one: Fe3P2 the charge on iron is a 2+ iron(II) phosphide Ions: O2- and Fe3+ What do we call the cation? What do we call the anion?

Practice Write the formula of the compound from the name: copper (II) nitrate gold (I) chromate Name the compound: FeO Zn(OH)2 CoPO4 iron (II) oxide zinc hydroxide cobalt (III) phosphate