- Chapter 3 – Molecules, Compounds, and Chemical Equations - Chemical Bonds o The Properties of the compound are totally different from the constituent elements.o Compounds are made of atoms held togethero Chemical Bonds are forces of attraction between atomso The bonding attraction comes from attractions between protons and electrons- Bonding Types o Two general types of bonding between atoms found in compounds, ionic and covalento Ionic Bonds – result when electrons have been transferred between atoms, resulting in oppositely charged ions that attract each other Generally found when metal atoms bond to nonmetal atoms Bonds form due to force of attraction between oppositely charged ionso Covalent Bonds – Result when two atoms share some of their electrons Generally found when nonmetal atoms bond together Bonds form between atoms by sharing electrons Resulting collection of atoms is called a molecule- Representing Compounds: Chemical Formula and Molecular Models o Chemical Formula indicates the elements present in the compound and the relative number of atoms or ions of eacho There are different types of chemical formula Empirical Formula – gives the relative number of atoms of each element in compound Molecular Formula – gives the actual number of atoms of each element in a molecule of a compound- Ex. Hydrogen Peroxide: Empirical Formula – HO Structural Formula – using lines represent the covalent bonds, shows atoms connection in molecular Molecular Models – Ball-and-Stick and space-filling- Classification of Elements and Compound o Elements may be either atomic or molecularo Compounds may be either molecular or ionico Atomic Element – exists in nature with single atom as its basic unit (He, Fe)o Molecular Elements – Exist in nature as molecules, when two or atoms are bonded togethero Molecular Compounds – Composed of two or more covalently bonded nonmetalso Ionic Compounds – Composed of cations and anions bounded together by ionic bonds. Basic unit of I.C. is the formula unit, the smallest, electrically neutral collection of ions- Compounds that Contain Ions o Compound must have no total charge, therefore we must balance the numbers of cations and anions in a compound to get 0 chargeo If Na+ is combined with S2-, you will need two Na+ ions for every S2- ion to balance the charges, therefore the formula must beNa2S- Naming Monatomic Nonmetal Anion o Determine the charge from position on the PeriodicTableo To name anion, change ending on the element to –ide- Polyatomic Ions o Polyatomic ions are single ions that contain more than one atomo Often identified by parentheses around ion in formulao Name and charge of polyatomic ion do not changeo Name any ionic compound by naming cation first then anion- Common Polyatomic Ions- Patterns for Polyatomic Ionso Elements in the same column form similar polyatomic ionso If the polyatomic ion starts with H, add hydrogen-prefix before the name and add 1 to the charge- Writing Formula for Ionic compounds containing polyatomic ion (Iron (III) Phosphateo Write the Symbol for the cation and its’ chargeo Write the symbol for the anion and its’ chargeo Charge (without sign) become subscript for otheriono Reduces subscripts to smallest whole numberratioo Check the total charge of the cations cancels thetotal charge of anions- Hydrates o Hydrates are ionic compounds containing a specific number of waters for each formula unito Water of hydration often “driven off” by heatingo In formula, attached waters follow o In name attached waters indicated by Prefix + hydrate after name of ioniccompound - Naming Binary Molecular o 1. Name the Elemento 2. Name the Second Element with an –ideo 3. Add a prefix to each name to indicate the subscripto Write the first element with prefix, then the second element with prefix Drop prefix mono from first element+- Subscript – Prefixes o 1 = mono Not used on first nonmetalo 2 = di-o 3 = tri-o 4 = tetra-o 5 = penta-o 6 = hexa-o 7 = hepta-o 8 = octa-o 9 = nona-o 10 = deca-- Acidso Contain H+1 cation and anion In aqueous solutiono Binary acids have H+1 cation and nonmetal aniono Oxyacids have H+ cation and polyatomic anion- Naming Binary Acids o 1. Identify the aniono 2. Name the anion with an –ic suffixo 3. Add a hydro- prefix to the anion nameo 4. Add the word acid to the end- Naming Oxyacids o If polyatomic ion name ends in –ate, then change ending to –ic suffixo If polyatomic ion name ends in –ite, then change ending to –ous suffixo Write word acid at end of all names- Writing Formula for Acids o When name ends in acid, formulas starts with Ho Write formulas as if ionic, even though it is molecularo Hydro prefix means it is binary acid, no prefix means it is an oxyacido For oxyacid, if ending is –ic, polyatomic ion ends in –ate; if ending is –ous, polyatomic ion ends in –ous- Binary Acids o 1. Write the symbol for the Cation and its chargeo 2. Write the symbol for the anion and its chargeo 3. Charge (without sign) becomes subscript for other iono 4. Add (aq) to indicate dissolved o 5. Check that the total charge of the cations cancels the total charge of the anions- Formula Mass o The mass of an indivudal molecule or formula unit Also known as molecular mass of molecular weighto Sum of the masses of the atoms in a single molecule or formula unit Whole = sum of the parts- Percent Composition o Percentage of each elementin a compound By masso Can be determined from: The formula of thecompound The experimental mass analysis of thecompoundo The percentages may not always total to 100% due to rounding - Mass Percent as a Conversion Factor o The mass percent tells you the mass of a constituent element in 100g of the compound The fact that CCl2F2 is 58.64% Cl by mass means that 100g of CCl2F2 contains 58.64g CLo This can be used as a conversion factor 100g CCl2F2 : 58.64g Cl- Finding an Empirical Formula o 1. Convert the percentages to grams Assume you start with 100g of the compound Skip if already in gramso 2. Convert grams to moles Use molar mass of each elemento 3. Write a pseudo formula using moles as subscriptso 4. Divide all by smallest number of moles If result is within .1 of whole number, round to whole numbero 5. Multiply all mole ratios by number to make all whole numbers If ratio ? (unknown) .5, multiply all by 2;