Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Atoms, Molecules and Ions John Dalton 1806 Atomic Theory of Matter 1. Matter consists of indivisible atoms 2. All atoms of a given element have identical properties 3. Different elements have atoms that differ in mass 4. Atoms are indestructible and chemical reactions are a rearrangement of atoms 5. Compounds contain a definite and small number of atoms 1. Matter consists of indivisible atoms subatomic particles 1. electrons 2. protons 3. neutrons electrons charge = -1.60 x 10-19 C = -1 mass = 9.1 x 10-31 kg protons charge = +1 mass = 1.673 x 10-27 kg neutrons charge = 0 mass = 1.675 x 10-27 kg 1. Matter consists of indivisible atoms nucleus = protons + neutrons electrons move around the nucleus electron “cloud” = volume of atom average diameter of atom 10-10 m = ångström (Å) 2. All atoms of a given element have identical properties ? not exactly A ZX atoms of an element = same number of protons atomic number = Z Z = 6 = C carbon Z = 30 = Zn zinc 6C 30Zn 6 e30 e- elements neutral # protons = # eelements different # neutrons proton + neutron = A = mass number 2. All atoms of a given element have identical properties element can have isotopes carbon Z = 6 A ZX 7 nuclides of C 12 C 6 most abundant 6 neutrons Carbon-14 dating 6 protons + 8 neutrons 14 C 6 What is the symbol for a nuclide that contains 22 neutrons and 18 protons? 40 18 Ar 4. Atoms are indestructible and chemical reactions are a rearrangement of atoms reactions involve valence electrons valence e- = Group number 1 8 2 3 4 5 6 7 1 8 2 3 4 5 6 7 non-metals metals elements arranged by atomic number column group chemical properties row period are determined by an element’s group Noble gases unreactive 8 valence electrons (He 2 valence e-) monatomic gases Alkali metals soft solids very, very reactive 1 valence electron lose 1 electron + Na ( 11 protons, 10 e-) Na (11 protons, 11 e ) cation Alkaline earth metals solids reactive 2 valence electrons Sr Sr2+ 7 lose 2 electrons Halogens very reactive 7 valence electrons Cl (17 protons, 17 e -) gain 1 electron - Cl (17 protons, 18 e-) anion Properties of Metals Good conductors of heat and electricity Solids Lose e- to form cations Properties of Non-metals Poor conductors of heat and electricity Solids, liquids and gases 5 3 4 B C N Gain e- to form anions 5 6 Si 14 P 6 7 7 O 15 S 16 Cl 17 Se34 Br35 Te52 I 53 As33 = metalloids 8 F 9 At85 H1 doesn’t fit anywhere lose eH (1 proton, 1 e-) gain eH (1 proton, 1 e-) + H (1 proton, 0 e-) proton H (1 proton, 2 e-) hydride 5. Compounds contain a definite and small number of atoms Ionic solids include a metal and a non-metal cation + anion Æ neutral molecule + sodium + chlorine Na+ Cl - NaCl sodium chloride lithium + oxygen 2Li + O Li 2 O lithium oxide magnesium + nitrogen Mg 3 N2 magnesium nitride Mg 2+ N3strong interactions (ion-ion) Æ high melting points (801o C for NaCl; >1700o C for Li2O) Transition metals more than 1 form except Ag+, Zn2+, Cd2+, Al3+ aluminum+ sulfur Al3+ S2Al2 S 3 aluminum sulfide manganese + oxygen Mn1+ Mn2+ Mn3+ Mn4+ Mn4+ O2MnO2 manganese(IV) oxide Covalent compounds non-metal + non-metal share valence electrons = chemical bonds carbon + chlorine 1 mono 4+ Cl C 2 di 3 tri CCl4 4 tetra carbon tetrachloride 5 penta nitrogen + oxygen ? N O 2(2+) NO nitrogen monoxide (4+) NO2 nitrogen dioxide (4+) N2O4 dinitrogen tetroxide 6 7 8 hexa hepta octa More covalent compounds N 3+ H1- NH3 nitrogen trihydride ammonia H 1+ O2- H2O dihydrogen monoxide water weak forces Æ low m.p. (0.0o C for water) Table 2.5 p. 62 Polyatomic ions NH4+ OHNO3SO42PO43- ammonium hydroxide nitrate sulfate phosphate ClO3MnO4CrO42CO32- chlorate permanganate chromate carbonate