Atoms, Molecules, and Ions Ch. 2 (cont.)
HW 2 2. Aluminum is a lightweight metal (ρ=2.70 g/cm3) used in aircraft construction, high-voltage transmission lines, and foils. What is its density in kg/m3? 2.70 x 103 kg/m3
HW 2 3. A resting adult requires about 240 mL of pure oxygen/min and breathes about 12 times every minute. If inhaled air contains 20% oxygen by volume and exhaled air 16%, what is the volume of air per breath? (Assume that the volume of inhaled air is equal to that of exhaled air.) • Need volume of O2 required per breath • Need % O2 used • Use above to figure out volume of air per breath
HW 2 3. A resting adult requires about 240 mL of pure oxygen/min and breathes about 12 times every minute. If inhaled air contains 20% oxygen by volume and exhaled air 16%, what is the volume of air per breath? (Assume that the volume of inhaled air is equal to that of exhaled air.) 5.00 x 102 mL/breath
HW 2 5. What is the mass number of an iron atom that has 28 neutrons? 54 Fe 26
Q 1 • An object, of density 5.40 g/cm3 and mass 80.0 g, is dropped into a 100-mL graduated cylinder containing exactly 50.0 mL of water. To what height will the water level rise in the cylinder? • What subatomic particle(s) make up most of the mass of an atom? 64.8 mL protons and neutrons
hydrogen • What element listed in Group IA is not an alkali metal?
helium • What noble gas has a mass number of 4?
molecular empirical H2O A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance An empirical formula shows the simplest whole-number ratio of the atoms in a substance H2O CH2O C6H12O6 O3 O N2H4 NH2 2.6
ionic compounds consist of a cation and an anion • the formula is always the same as the empirical formula • the sum of the charges on the cation and anion in each formula unit must equal zero The ionic compound NaCl 2.6
Formulas of ionic compounds 2 x +3 = +6 1 x +2 = +2 1 x +2 = +2 1 x -2 = -2 2 x -1 = -2 3 x -2 = -6 Al2O3 Al3+ O2- CaBr2 Ca2+ Br- Na2CO3 Na+ CO32- 2.6
Some Polyatomic Ions (Table 2.3) Memorize the polyatomic ions (names and formulae) in Table 2.3 (p. 44, Chang)! 2.7
Write the formula for the compound that results when NH4 and SO4 ions associate. Is this a molecular formula or an empirical formula? NH4 has +1 charge SO4 has -2 charge (NH4) (SO4) 2 1 (NH4)2SO4 ammonium sulfate (from Table 2.3) ionic compound -> empirical formula
Nomenclature • Figure 2.13 (p.47, Chang) • Ionic • Cation has only one charge • Cation has more than one charge • Molecular
Nomenclature of ionic compounds The first element in the formula is identified by its English name, the second by appending the suffix –ide to its stem Chemical Name as Name as Symbol Stem First Element Second Element O ox- oxygen oxide S sulf- sulfur sulfide N nitr- nitrogen nitride P phosph- phosphorus phosphide F fluor- fluorine fluoride Cl chlor- chlorine chloride Br brom- bromine bromide I iod- iodine iodide *Note that element can be atomic or polyatomic; first element usually refers to the cation and second element usually refers to the anion
Nomenclature of ionic compounds • Ionic Compounds • often a metal + nonmetal • anion (nonmetal), add “ide” to stem barium chloride BaCl2 potassium oxide K2O magnesium hydroxide Mg(OH)2 potassium nitrate KNO3 2.7
Transition metal ionic compounds • recall that the charge on transition metals can vary • indicate charge on metal with Roman numerals (Stock system) • figure out charge by looking at overall anionic charge iron(II) chloride FeCl2 2 x Cl- = -2; so Fe is +2 FeCl3 3 x Cl- = -3; so Fe is +3 iron(III) chloride Cr2S3 3 x S-2 = -6 so Cr is +3 (6/2) chromium(III) sulfide 2.7
Nomenclature of molecular compounds • as a general rule, molecular compounds are formed when nonmetallic elements combine (sometimes a nonmetal and a metalloid) • nonmetals or nonmetals + metalloids • element further left in periodic table is 1st • element closest to bottom of group is 1st • if more than one compound can be formed from the same elements, use Greek prefixes to indicate number of each kind of atom • last element ends in ide 2.7
Nomenclature of molecular compounds • Many molecular compounds contain hydrogen: Group Noble Period IVA VA VIA VIIA Gas 2 CH4 NH3 H2O HF Ne 3 SiH4 PH3 H2S HCl Ar 4 GeH4 AsH3 H2Se HBr Kr 5 SbH3 H2Te HI Xe Note: The number of hydrogens that combined with the nonmetal equals the number of spaces to the right we have to move to get to the noble gas
Nomenclature of molecular compounds Greek Prefixes mono- = 1 (often omitted) hexa- = 6 di- = 2 hepta- = 7 tri- = 3 octa- = 8 tetra- = 4 nona- = 9 penta- = 5 deca- = 10 • The number of each type of atom is specified with Greek prefixes Examples: PF5 = phosphorus pentafluoride HCl = hydrogen chloride N2O5 = dinitrogen pentoxide Note: many compounds have common names, like water for H2O.
Molecular compounds TOXIC! Laughing Gas HI hydrogen iodide NF3 nitrogen trifluoride SO2 sulfur dioxide N2Cl4 dinitrogen tetrachloride NO2 nitrogen dioxide N2O dinitrogen monoxide 2.7
nitric acid HNO3 H2CO3 carbonic acid HClO3 chloric acid H2SO4 sulfuric acid An acid can be defined as a substance that yields hydrogen ions (H+) when dissolved in water. • HCl • Pure substance, hydrogen chloride • Dissolved in water (H+ Cl-), hydrochloric acid An oxoacid is an acid that contains hydrogen, oxygen, and another element (see section 2.7 & Tables 2.5 and 2.6… memorize these). 2.7
Naming oxoacids & oxoanions HClO4 (perchloric acid) ClO4-(perchlorate) HClO3 (chloric acid) ClO3-(chlorate) HClO2 (chlorous acid) ClO2-(chlorite) HClO(hypochlorous acid) ClO-(hypochlorite) 2.7
Practice with oxoacids • Name HNO3, HNO2, HNO • Write formulas for sulfuric acid and sulfurous acid (stem= sulf-) • Name the anions of HNO3, HNO2, HNO • Name the anions of sulfuric acid and sulfurous acid