Presentation on theme: "Topic: Writing Binary Ionic Formulas"— Presentation transcript:
1 Topic: Writing Binary Ionic Formulas Do Now: An atom of which element has the greatest attraction for electrons in a chemical bond?AsGaGeSe
2 Empirical Formulas= smallest whole-number ratio of elements in compoundIonic compounds have empirical formulas only
3 Identify the empirical formulas H2OH2O2CaF2NaClCH4C2H6NiOFeCl3Empirical – NOT ionicMolecular – NOT ionicEmpirical, IonicEmpirical, IonicEmpirical – NOT ionicMolecular – NOT ionicEmpirical, IonicEmpirical, Ionic
4 Formula Unit = simplest ratio of ions in ionic compound Examples: KBr is formula unitpotassium ions & bromide ions are in a 1-to-1 ratioAl(NO3)3 is formula unitAluminum & nitrate ions in 1-to-3 ration
5 Binary Ionic Compounds Composed of two different elementsPositive monatomic metal ionNegative monatomic nonmetal ionNote: A binary compound may contain more than 2 ions but only 2 kinds of ions like Al2O3
6 Oxidation Number or State Na+1charge of monatomic ionhas right superscriptSome elements form only 1 ionSome elements can form more than 1 ionCa+2O-2Al+3 and Ag+1Fe+2 and Fe+3
7 Oxidation States Group 1 ions always +1 Group 2 ions always +2 MOST group 13 ions are +3Groups 14, 15, 16, and 17 have multiple oxidation statesboth (+) and (-)Transition metals (Group B) can have more than 1 oxidation statebut are always (+)
8 Writing Formulas for Binary Ionic Compounds first rule in writing formulas for ionic compounds isPOSITIVE ION FIRSTBut how do you get the subscripts?start by writing formulas from the ions
9 Compounds are electrically neutral Sum of all charges in compoundshould be 0(+) and (-) charges must = each other
10 Equal but Opposite Charges Na+1 and Cl-1: NaCl (-1) = 0Mg+2 and O-2: MgO (-2) = 0Al+3 and P-3: AlP (-3) = 0Rule: write symbols, (+) FIRST!
11 Try a few formulas: Li+1 and I-1 Ca+2 and O-2 Al+3 and N-3 K+1 and F-1 Ba+2 and S-2LiICaOAlNKFBaS
12 Criss-Cross Method When the charges don’t cancel out immediately: Mg+2 and Cl-1, CROSS and DROP!(# only, forget signs!)Mg1Cl2 but if subscript is 1, forget it!MgCl2 means 1 Mg+2 and 2 Cl-1
13 Check the Math MgCl2 means 1 Mg+2 and 2 Cl-1 (1 x +2) + (2 x -1) = = 0charges MUST add up to zero!
15 Of course, it gets more difficult Potassium (K) and Fluorine (F)Zinc (Zn) and Iodine (I)Sodium (Na) and Oxygen (O)Magnesium (Mg) and Oxygen (O)Aluminum (Al) and Oxygen (O)Calcium (Ca) and Bromine (Br)Cesium (Cs) and Iodine (I)Silver (Ag) and Sulfur (S)KFZnI2Na2OMgOAl2O3CaBr2CsIAg2S