Presentation on theme: "Molecules, Ions and Their Compounds"— Presentation transcript:
1Molecules, Ions and Their Compounds AP Notes Chapter 2Molecules, Ions and Their Compounds
2Chemical CompoundsChemical compounds result from the joining together of atomsChemical Bonds are the forces that hold atoms together.Chemical formulas are used to describe the number and kind of atoms in a compoundThere are two major types of compounds that differ mostly by the way the atoms hold on to each other or the type of bond.
3Ionic CompoundsIonic compound are held together with an Ionic bond joining metal ions and non metal ionsTransfer of electrons cause the formation of ions or charged particles
4Ions & Ionic Compounds Atoms or groups of atoms with a charge. Cations- positive ions - get by losing electrons(s). MetallicAnions- negative ions - get by gaining electron(s). NonmetallicIt is these opposite charges that define an ionic compound and an ionic bondSolid Ionic compounds are called salts.
6Ionic CompoundsLaw of Definite Proportion- compounds have a constant composition.Ions react in specific ratios by mass and charge.Ionic compounds do not have a chargePositive and negative charges balanceIons exist in small whole number ratios.Get charges from table, name of metal ion, or memorized from the list.Use parenthesis to indicate multiple polyatomics.
7Naming Ionic Compounds Cation is wrtiten first in name and formula.If the cation is monoatomic- Name the metal (cation) just write the name.If the cation is polyatomic- name it.THEN If the anion is monoatomic- name it but change the ending to –ide.If the anion is poly atomic- just name itPractice Ion names and formula w/charge
8Naming Ionic Compounds Have to know what ions they formoff table, polyatomic, or figure it outCaSK2SAlPO4K2SO4FeSCoI3Calcium sulfidePotassium sulfideAluminum phosphatePotassium sulfateIron II sulfideor Ferrous sulfideCobalt III iodideor Cobaltic iodide
10Writing Ionic Formulas Sodium nitridesodium- Na is always +1Nitride - ide tells you it comes from the tablenitride is N-3Doesn’t add up to zero.Na+1N-3
11Writing Ionic Formulas Sodium nitridesodium- Na is always +1nitride - ide tells you it comes from the tablenitride is N-3Doesn’t add up to zeroNeed 3 NaNa+1N-3Na3N
12Ionic Compound Formulas Sodium sulfitecalcium iodideLead (II) oxideLead (IV) oxideMercury (I) sulfideBarium chromateAluminum hydrogen sulfateCerium (IV) nitriteNa2SCaI2PbOPb2O4 or PbO2Hg2SBaCrO4Al(HSO4)3Ce(NO3)4
13Covalent Compounds Composed of Molecules Law of Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers.Chemical formula- the number and type of atoms in a molecule.C2H6 - 2 carbon atoms, 6 hydrogen atomsStructural formula shows the connections, but not necessarily the shape.
14Molecules differ by the number and kind of elements that make them up Speculate on the formula of two oxides of carbon and oxygenCarbon monoxide =Carbon dioxide =Show that these compounds follow the law of multiple proportion.Sometimes formula is not enough to get an adequate picture of a compoundCOCO2
15There are also other models that attempt to show three dimensional shape. Ball and stick.HHHCCHHHBall and stick.
16Covalent compounds Two words, with prefixes. Prefixes tell you how many.mono, di, tri, tetra, penta, hexa, septa, nona, decaFirst element whole name with the appropriate prefix, except mono.Second element, -ide ending with appropriate prefix.Practice
17Naming Covalent Compounds Two words, with prefixesPrefixes tell you how many.mono, di, tri, tetra, penta, hexa, septa, nona, decaFirst element whole name with the appropriate prefix, except monoSecond element, -ide ending with appropriate prefixPractice
19Covalent compounds The name tells you how to write the formula Sulfur dioxidedifluorine monoxidenitrogen trichloridediphosphorus pentoxide
20Summary for Writing Formulas and Names of Compounds Two sets of rules, ionic and covalentTo decide which to use, decide what the first word is.If is a metal or polyatomic use ionic.If it is a non-metal use covalent.
21Acids Substances that produce H+ ions when dissolved in water. All acids begin with H.Two types of acids:OxyacidsNon-oxyacids
22Naming acids If the formula has oxygen in it write the name of the anion, but changeate to -ic acidite to -ous acidWatch out for sulfuric and sulfurousH2CrO4HMnO4HNO2
23Naming acids If the acid doesn’t have oxygen add the prefix hydro- change the suffix -ide to -ic acidHClH2SHCN
24Formulas for acids Backwards from names. If it has hydro- in the name it has no oxygenAnion ends in -ideNo hydro, anion ends in -ate or -iteWrite anion and add enough H to balance the charges.
26Percent Composition Percent of each element a compound is composed of. Find the mass of each element, divide by the total mass, multiply by a 100.Easiest if you use a mole of the compound.Find the percent composition of CH4Al2(Cr2O7)3CaSO4 · 2H2O
27Working backwardsFrom percent composition, you can determine the empirical formula.Empirical Formula the lowest ratio of atoms in a molecule.Based on mole ratios.A sample is 59.53% C, 5.38%H, 10.68%N, and 24.40%O what is its empirical formula.
28Sample ProblemA gram sample of a compound (vitamin C) composed of only C, H, and O is burned completely with excess O g of CO2 and g of H2O are produced. What is the empirical formula?
29Empirical To Molecular Formulas Empirical is lowest ratio.Molecular is actual molecule.Need Molar mass.Ratio of empirical to molar mass will tell you the molecular formula.Must be a whole number because...
30Sample ProblemA compound is made of only sulfur and oxygen. It is 69.6% S by mass. Its molar mass is 184 g/mol. What is its formula?
31Hydrates Some salts trap water crystals when they form crystals. These are hydrates.Both the name and the formula needs to indicate how many water molecules are trapped.In the name we add the word hydrate with a prefix that tells us how many water molecules.
32HydratesIn the formula you put a dot and then write the number of molecules.Calcium chloride dihydrateChromium (III) nitrate hexahydrateCaCl2·2H2OCr(NO3)3· 6H2O