Atoms, Molecules and Ions Atomic Theory of Matter John Dalton 1806 1. Matter consists of indivisible atoms All atoms of a given element have identical properties 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 electrons protons neutrons subatomic particles 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)

? = Z # protons = # e- 2. All atoms of a given element have identical properties X A Z ? not exactly atoms of an element = same number of protons atomic number = Z Z = 6 = C carbon 6C 6 e- Z = 30 = Zn zinc 30Zn 30 e- elements neutral # protons = # e- elements different # neutrons proton + neutron = A = mass number

Ar 40 18 2. All atoms of a given element have identical properties X A Z element can have isotopes 7 nuclides of C carbon Z = 6 6C 12 most abundant 6 neutrons Carbon-14 dating C 14 6 6 protons + 8 neutrons What is the symbol for a nuclide that contains 22 neutrons and 18 protons? Ar 40 18

4. Atoms are indestructible and chemical reactions are a rearrangement of atoms reactions valence electrons valence e- = Group number 1 8 2 3 4 5 6 7

elements arranged by atomic number column group chemical properties 1 2 3 4 5 6 7 8 elements arranged by atomic number column group chemical properties row period

Noble gases Alkali metals unreactive 8 valence electrons (He 2 valence e-) monatomic gases Alkali metals soft solids very, very reactive 1 valence electron lose 1 electron Na ( protons, e-) 11 11 Na ( protons, e-) 11 + 10 cation

Alkaline earth metals solids reactive 2 valence electrons lose 2 electrons Sr Sr2+ conduct heat, electricity solids (Hg) lose e- non-metals metals

Non-metals = metalloids poor conductors solids, liquids, gases Group 7 Si 14 C 6 B 5 N 7 O 8 F 9 P 15 S 16 Cl 17 As33 Se34 Br35 Te52 I 53 At85 3 4 5 6 7 = metalloids poor conductors solids, liquids, gases Group 7 halogens X2 very reactive 7 valence electrons gain 1 electron Cl ( protons, e-) 17 17 Cl ( protons, e-) 17 - 18 anion non-metals gain electrons

doesn’t fit anywhere lose e- H ( proton, e-) 1 1 H ( proton, e-) 1 + + gain e- proton H ( proton, e-) 1 H ( proton, e-) 1 2 - hydride

Ionic solids cation + anion + - metal non-metal sodium + chlorine NaCl 5. Compounds contain a definite and small number of atoms Ionic solids cation + anion + - metal non-metal sodium + chlorine NaCl sodium chloride Na Cl + - 801o C lithium + oxygen Li O lithium oxide Li O 2 + 2- > 1700oC magnesium + nitrogen Mg N magnesium nitride Mg N 2+ 3- 3 2 strong interactions (ion-ion) high melting points

Transition metals more than 1 form except Ag+ Zn2+ Cd2+ Al3+ aluminum manganese + oxygen + sulfur Al Mn1+ Mn2+ Mn3+ Mn4+ S 3+ 2- Al S 2 3 aluminum sulfide Mn3+ O 2- Mn2O3 Mn4+ O2- MnO2 manganese (III) oxide manganese (IV) oxide

share valence electrons = chemical bonds carbon + chlorine C Cl 4+ - Covalent compounds non-metal + non-metal share valence electrons = chemical bonds carbon + chlorine mono di tri tetra penta hexa hepta octa C Cl 4+ - CCl4 carbon tetra chloride nitrogen + oxygen N ? O 2- NO nitrogen monoxide 2+ NO2 nitrogen dioxide 4+ N2O4 dinitrogen tetroxide 4+

Covalent compounds N H NH3 nitrogen trihydride ammonia 3+ 1- H O H2O dihydrogen monoxide water 1+ 2- weak forces low m.p. 0.0oC Table 2.5 p. 62 Polyatomic ions NH4+ ammonium ClO3- chlorate OH- hydroxide MnO4- permanganate NO3- nitrate CrO42- chromate SO42- sulfate CO32- carbonate PO43- phosphate