Presentation on theme: "Representing Chemical Compounds"— Presentation transcript:
1Representing Chemical Compounds Naming Compounds and Writing Chemical Formulas
2Chemical FormulaShows the kinds and numbers of atoms in the smallest representative unit of the substance.If only one atom of the element in a compound, you only write the element’s symbol. (Ex: Lithium fluoride LiF)If the molecules of the element each have more than one atom, a number is used as a subscript. (Ex: Lithium oxide Li2O).
3Molecular FormulasChemical formula for a molecular compound is called a molecular formula.Shows the kinds and numbers of atoms present in a molecule of a compound.Examples: CO, CO2Tells nothing about the structure of the molecule --- doesn’t show arrangement of the various atoms.
4Molecular Formulas (continued) Refer to page 129, Figures 6.6 – 6.8.Use models and/or diagrams to show the arrangements of molecules in a molecular compound.IMPORTANT NOTE: Be familiar with the various types of representations of molecular compounds: Molecular formula, Space-filling molecular model, Perspective Drawing, Ball-and-Stick Molecular Model.
5Formula Units Chemical formulas represent ionic compounds. Formula units – lowest whole-number ration of ions in the compound.
6Laws of Definite and Multiple Proportions Law of Definite Proportions: in samples of any chemical compound, the masses of the elements are always in the same proportions.Law of Multiple Proportions: whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.Refer to page 142, Practice Problems.
7Ionic ChargesFor most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location.Elements in the same group have similar properties.Including the charge when they are ions.
9Naming ions We will use the systematic way. Cation- if the charge is always the same (Group A) just write the name of the metal.Transition metals can have more than one type of charge.Indicate the charge with roman numerals in parenthesis.
17Naming Binary Ionic Compounds Binary Compounds - 2 elements.Ionic - a cation and an anion.To write the names just name the two ions.Easy with Representative elements.Group ANaCl = Na+ Cl- = sodium chlorideMgBr2 = Mg+2 Br- = magnesium bromide
18Naming Binary Ionic Compounds The problem comes with the transition metals.Need to figure out their charges.The compound must be neutral.same number of + and – charges.Use the anion to determine the charge on the positive ion.
19Naming Binary Ionic Compounds Write the name of CuONeed the charge of CuO is -2copper must be +2Copper (II) chlorideName CoCl3Cl is -1 and there are three of them = -3Co must be +3 Cobalt (III) chloride
20Naming Binary Ionic Compounds Write the name of Cu2S.Since S is -2, the Cu2 must be +2, so each one is +1.copper (I) sulfideFe2O3Each O is x -2 = -63 Fe must = +6, so each is +2.iron (III) oxide
21Naming Binary Ionic Compounds Write the names of the followingKClNa3NCrNSc3P2PbOPbO2Na2Se
22Ternary Ionic Compounds Will have polyatomic ionsAt least three elementsname the ionsNaNO3CaSO4CuSO3(NH4)2O
24Writing Formulas The charges have to add up to zero. Get charges on pieces.Cations from name of table.Anions from table or polyatomic.Balance the charges by adding subscripts.Put polyatomics in parenthesis.
25Writing Formulas Write the formula for calcium chloride. Calcium is Ca+2Chloride is Cl-1Ca+2 Cl-1 would have a +1 charge.Need another Cl-1Ca+2 Cl 2-
26Write the formulas for these Lithium sulfidetin (II) oxidetin (IV) oxideMagnesium fluorideCopper (II) sulfateIron (III) phosphidegallium nitrateIron (III) sulfide
27Write the formulas for these Ammonium chlorideammonium sulfidebarium nitrate
28Things to look for If cations have (), the number is their charge. If anions end in -ide they are probably off the periodic table (Monoatomic)If anion ends in -ate or -ite it is polyatomic
29Writing names and Formulas Molecular CompoundsWriting names and Formulas
30Molecular compounds made of just nonmetals smallest piece is a moleculecan’t be held together because of opposite charges.can’t use charges to figure out how many of each atom
31Easier Molecular compounds name tells you the number of atoms. Ionic compounds use charges to determine how many of each.Have to figure out charges.Have to figure out numbers.Molecular compounds name tells you the number of atoms.Uses prefixes to tell you the number
38Write formulas for these diphosphorus pentoxidetetraiodide nonoxidesulfur hexaflouridenitrogen trioxideCarbon tetrahydridephosphorus trifluoridealuminum chloride
39Writing names and Formulas AcidsWriting names and Formulas
40Acids Compounds that give off hydrogen ions when dissolved in water. Must have H in them.will always be some H next to an anion.The anion determines the name.
41Naming acidsIf the anion attached to hydrogen is ends in -ide, put the prefix hydro- and change -ide to -ic acidHCl - hydrogen ion and chloride ionhydrochloric acidH2S hydrogen ion and sulfide ionhydrosulfuric acid
42Naming Acids If the anion has oxygen in it it ends in -ate of -ite change the suffix -ate to -ic acidHNO3 Hydrogen and nitrate ionsNitric acidchange the suffix -ite to -ous acidHNO2 Hydrogen and nitrite ionsNitrous acid