Molecules What are Molecules Molecules are from a combination of two or more atoms joined together by chemical bonds Molecules of an element consist of one type of atom O2 or O3 Molecules of a compound consist of two or more different kinds of atoms Kind and quantity of each atom present in a molecule or formula unit of substance Examples o Show the order in which the atoms are bonded may or may not indicate the actual shape H2O Chemical Formula H O H Structural Formula Types of Formulas Chemical Formulas o Describe chemical composition Structural Formulas P4 C2H5OH of the molecule Examples Ball and Stick and Space Filling Models Shows o Bonding sequence o Geometrical arrangement What are Ionic Compounds Ionic compounds bond due to ion formation than opposites attracting They result from a combination of anions and cations to form neutral species held together by Ball and Stick Model Space Filling Models electrostatic forces Electrons released Electrons Absorbed MEMORIZE THESE 10 IONS Formula Unit lowest whole number ratio o Zn2 Zinc ion o Ag Silver ion o NH4 o CO3 o NO3 o PO4 o SO4 o ClO3 o C2H3O2 Ammonium 2 Carbonate Nitrate 3 Phosphate 2 Sulfate Chlorate Acetate o OH Hydroxide Naming I Metal Nonmetal a Name of metal root of nonmetal ide Periods 1 2 3 II Variable Valence Metal Nonmetal a Name of metal charge in Roman numerals root of nonmetal ide b MOST transition metals c A Roman numeral in parentheses following the name of the metal indicates the oxidation The old method uses the suffixes ous and ic to indicate lower and higher oxidation states III Polyatomic ions IV Naming Binary Molecular Compounds a Nonmetal Nonmetal a Can replace the metal the root of the nonmetal ide in I or II above i Prefix of 1st element if 1 name of 1st element prefix of 2nd element root of 2nd ii THE MORE METALLIC ELEMENT IS NAME FIRST HIGHEST ELECTRONEGATIVITY element ide LAST V Naming Oxoanions a Special type of polyatomic ions i Memorize the ate form Nitrate ii Remove 1 O to get the ite form Nitrite iii Remove another O to get the hypo ite form Hyponitrite iv Add 1 O to get the per ate form Pernitrate VI Naming Acids have H with a nonmetal or polyatomic a H with a nonmetal Binary Acid i hydro root of nonmetal ic Acid 1 HCl hydrochloric acid b H with the ate form of the polyatomic Ternary Acid i root of nonmetal ic Acid 1 HClO3 chloric acid c H with the ite form of the polyatomic i root of nonmetal ous Acid 1 HClO2 Chlorous Acid d H with the hypo ite form of the polyatomic i hypo root of nonmetal ous Acid 1 HNO hyponitrous acid e H with the per ate form of the polyatomic i per root of nonmetal ic acid 1 HNO4 pernitric acid Mass and Weight Atomic Mass Weight AM o Average Mass of the atoms of an element based on the atomic mass unit o Calculating Atomic Mass Atomic Mass Fractional abundance x Isotopic Mass Atomic Mass Unit amu o Defined as exactly 1 12 of the mass of an atom of C 12 Formula Weight or Formula Mass FW o Used for compounds regardless of the bonding o Obtained by summing the atomic masses of each of the elements in the chemical formula Molecular Weight Molecular Mass MW o Used for nonionic compounds covalent bonding or compounds made of nonmetals o MW of a compound is obtained by summing the atomic weights of each of the elements in the chemical formula Molar Mass o Mass of 1 mole o MM of an element in g mol is numerically equal to the atomic weight of the element in o MM of a compound is obtained by summing the atomic weights of each of the elements in amu atom the chemical formula Avogadro s Number 6 022 E 23 Avogadro suggested that equal volumes of all gases a the same temperature and pressure contain the same number of molecules which is now known as Avogadro s Principle Mole mol 6 022E23 or Avogadro s number of particles Percent Composition If the chemical formula of a compound is known its chemical composition can be expressed as the percent composition by mass of each element in the compound o A in compound mass A in 1 mole of Compound Mass of 1 mole of compound X 100 Formulas Most often chemist knows composition but formula is unknown Empirical Formula o Lowest whole number ration of elements in the compound o Steps to Determine empirical formula 1 Determine mass of each element in 100 g of compound if given or the mass will be given 2 Determine moles of each element 3 Divide each number of moles by the smallest mole value 4 If whole number are obtained after appropriate rounding use as subscripts of the elements in the empirical formula If resulting numbers are not whole numbers multiply each number by an integer so that the results are whole numbers 5 o Plan grams moles mole ratio Molecular Formula the compound o Some multiple of the empirical formula shows actual numbers of atoms in a molecule of o Can be found if given the actual Molar Mass of the compound in addition to the composition info or empirical formula o Molecular Formula Mass Empirical Formula n o Molecular Formula Mass Empirical Formula Mass n Hydrated Compounds Have water incorporate in the formula The prefixes on hydrate are the same as those learned on nonmetal to nonmetal naming Must count water in molar mass Anhydrous means no water Example o Iron II Carbonate is FeCO3 o Iron II Carbonate Monohydrate is FeCO3 H2O Chemical Bonding Valence Electron Electrons in the outermost shell Determine physical and chemical bonding properties Stability with fully filled or half filled sublevel Nonmetals high EN gain e Metals low EN lose e Both form ions and bond by electrostatic attraction ionic bond Difference in EN of metal and nonmetal will be high indicating ionic bonding When EN difference is low no ions are formed Atoms pull about the same electrons are shared covalent bond Bonding Octet Rule When atoms bond they usually lose gain or share electrons to attain a noble gas configuration usually a filled outer shell of eight electrons Exceptions o H to B H He Li Be B who have less than 8 usually have the number of bonds equal to their valence electrons o 3rd period elements who can have more than 8 due to possible d orbitals Lewis Dot Formulas Bookkeeping of valence electrons Each valence electron represented by a dot Number of valence electrons Group number using A and B notation Single atoms show electron configuration in dots Lewis Formula Rules 1 Count the valence electrons a Find the sum of valence electrons of all atoms in the polyatomic ion or molecule i ii If it is an anion add one electron for each negative
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