Names and Formulas for Ionic Compounds

Names and Formulas for Ionic Compounds

Types of ions • Monatomic ion • ion with one atom • Mg2+ magnesium ion • Cl- chloride ion • Polyatomic ion • ion with more than one atom • NH4+ ammonium • NO3- nitrate

Ionic Compound Marriage Metals are like men Nonmetals are like woman Typically who changes their last name?

Naming Ca”t”ions • Monatomic cation name stays the same • Sodium, Na goes to sodium ion, Na+ • Calcium, Ca goes to calcium ion, Ca2+ • Polyatomic cation - look up in chart • NH4+ammonium

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

Question Time Given the neutral atom, give the charge and name of the monatomic ion that will form. (Look at periodic table group numbers for help.) • Na • Cl • Mg • S • P Na+ sodium cation Cl- chloride anion magnesium cation Mg2+ sulfide anion S2- phosphide anion P3-

Name the following polyatomic ions. (use your chart!) • NH4+ • OH− • SO32− • SO42− • CN− ammonium cation hydroxide anion sulfite anion sulfate anion cyanide anion

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

Will these form an Ionic Compound? If so what will the compound 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

Formula Unit • Formula Unit—the smallest whole number ratio of ions in a compound • NaCl versus Na2Cl2 • Correct: Sodium Chloride NaCl

What will the formula be? • In ionic compounds, we must balance charges to form a neutral compound • To do that, we “crisscross the charges” • Always reduce to get the formula unit Ca + N Ca2+ + N3- Ca3 N2 Both have a total charge of 6 (3 Ca2+ = +6; 2 N3- = -6)

Practice Given the following elements, predict the formula. (hint first identify the ion charge) • K, Br • Ca, Cl • Li, S • Mg, N • Ba, P

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 NO3- These charges do not balance so we must crisscross them Mg1(NO3)2 (we don’t need the 1) Mg(NO3)2

Transition Metal Ions • Metals 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

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

Question Time Identify the charge on the transition metal: • copper (II) nitrate • gold (I) chromate Name the compound: • FeO • Zn(OH)2 • CoPO4 2+ 1+ iron (II) oxide zinc hydroxide cobalt (III) phosphate

Names and Formulas for Ionic Compounds