Chapter #3: Molecules, Compounds, and Chemical Equations3.1 Hydrogen, Oxygen, and Water- Hydrogen is a explosive gas and Oxygen is not flammable but needs to be present for combustion.- Both have low boiling points. (gas)- Water (H2O) is nothing like its constituent elements. Liquid and smothers fire.- Compounds and its elements have very different properties.- Compounds has definite proportions while mixtures can mix in any proportion.3.2 Chemical Bonds- Compounds are atoms chemically bonded together.- Electrostatic forces create chemical bonds.- There are two types of chemical bonds: ionic bonds, and covalent bonds.Ionic Bonds- Metal tend to lose electrons and non-metals gain electrons.- Ionic bond is when a metal donates an electron to a non-metal.- Metal then becomes a cation and nonmetal becomes a anion and the ions are attracted to one another by electrostatic force.- Ionic compounds form a lattice structureCovalent Bond- Covalent bond is a bond between two non-metals where they share electrons.- Each covalent molecule is independent of other molecules.- Also called molecular compound.- In covalent bonds, electrons hold the elements together by attracting the positive nuclei.- Low potential energy and thus stable.- Lowest potential energy when a negative charge is between two positive.3.3 Representing CompoundsTypes of Chemical Formulas- Empirical formula provides the relative amount of atoms for each element in a compound.- Molecular formula provides the exact number of atoms for each element in a compound.- Structural formula shows the how atoms are bonded together in a compound.Molecular Models- Ball-and-stick molecular model shows the geometry of the molecule by using the sticks to show the bonds and ball to show the elements.- Space-filling molecular model shows how a molecule might be if it was visible.3.4 Classification of Pure Substances- Pure substances can either be elements or compounds.- Elements can be categorized as atomic elements or molecular elements.- Atomic elements exist as single atoms as their basic unit in nature.- Molecular elements exist as molecules composed of the same element as their basic unit in nature. (diatomic or polyatomic molecules)- Compounds can be either molecular or ionic compounds.- Molecular compounds are nonmetals covalently bonded together.- Ionic compounds are a metal (cation) and a nonmetal (anion) bonded together by ionic bonds. It exists as a lattice not discrete entity like molecular compounds.- Polyatomic ion is an ion composed of two or more atoms.3.5 Ionic CompoundsIonic Formulas- Ionic compounds are charge-neutral.- Ionic compounds always have positive and negative ions.- The sum of positive ions must equal sum of negative ions.- Formula is in smallest whole number ratio.Naming Ionic Compounds- There are two categories of metal for ionic compounds: metal forms one type of ion and metal forms more than one type of ion.- If metal forms more than one type of ion, it need to be specified with roman numerals after the name.- Binary ionic compounds with metal that forms only one ion can be named by stating the cation and then the anion with the suffix, -ide. (KCl - Potassium Chloride)- Binary ionic compounds with metal that forms more than one ion is the name of the cation with the charge in roman numeral followed by the anion with ending -ide.- If the ionic compound contains a polyatomic ion, name the polyatomic ion after the cation.Hydrated Ionic Compounds- Ionic compounds called hydrates contain water molecules with formula.- Waters of hydration can be removed by heating compound.- Add _____hydrate after compound name.- Prefixes for hydrate include heml (1/2), mono, di, tri, tetra, penta, hexa, hepta, octa.3.6 Molecular Compounds- Same combination of elements can form different compounds so naming is a bit different from ionic compound.Naming Molecular Compounds- Write the element with the smallest group number first.- If elements are in same group, write element with largest row number first.- If there is one atom of the first element, the prefix mono- can be omitted.- If there is one atom of the second element the prefix mono- has to be included. (e.x. carbon monoxide)- Use prefix mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca to indicate number of atoms present.Naming Acids- Acids release H+ ions when dissolved in water.- Acids are compose of hydrogen and two or more nonmetals. (H written first)- Aqueous solutions of compounds with H and nonmetals are acids.- Acids can be categorized as binary acids and oxyacids.- Binary acids are hydrogen and a nonmetal.- Use hydro(nonmetal with suffix -ic) acid to name compound. (e.x HBr- hydrobromic acid)- Oxyacids include hydrogen and oxyanion (nonmetal and oxygen).- If oxyanion ends with -ate, use name of oxyanion with suffix -ic acid.- If oxyanion ends with -ite, use name of oxyanion with suffix -ous acid.3.8 Formula Mass and Mole Concept for Compounds- Average mass of molecule is molecular mass.- Molecular mass is the sum of the masses of all atoms in molecule.- Molar mass of compound is molecular mass per mol.- Same concept and calculation for molecules as elements.3.9 Composition of Compounds- To calculate the percentage of an element in a molecule, divide total molar mass of element by molar mass of molecule.- To calculate amount (g) of element in a compound, use mass percent composition as a conversion factor.- Ratio of moles can also be used as a conversion factor to find amount of element in a compound.3.10 Chemical Formula from Experimental Data- Can determine empirical formula from percent composition of elements.- To find molecular formula, the molar mass is also needed.- Convert percentage and grams into moles to find ratio for empirical formula.- Put the obtained moles as the subscript of the element and divide all by the smallest mole.- If subscript after division is not a whole number, multiply all subscripts by a whole number so all subscripts are whole numbers.- For the molecular formula divide molar mass by empirical formula molar mass to find multiple.- Then multiply the multiple to all subscript in empirical formula Combustion Analysis- Used to determine an unknown substance.- In combustion, sample is burned and all carbon is converted to carbon dioxide and all hydrogen is converted to water.- Using mole ratio to find amount of carbon and hydrogen in original compound.- If there are other elements in compound other than carbon and hydrogen, subtract