Chapter Two: Atoms, Molecules & Ions  Atomic Theory & Structure  Isotopes, Numbers & Masses  Periodic Table  Molecules, Ions, Compounds & Formulas  Naming Species

Atomic Theory and Structure  What is the smallest piece of matter possible?  Democritus called the smallest particles “ atomos ”  Dalton’s atomic theory of matter: ­elements are composed of small particles -- atoms ­all atoms of an element are identical ­atoms are not created or destroyed chemically ­compounds formed by chemical combination of two or more elements ­a given compound has same relative number & type of atoms (law of constant composition) ­atoms retain character during chemical rxns. only undergo rearrangement (conservation of matter)

Law of Multiple Proportions If two elements, A & B, form more than one compound, the masses of B that can combine with a given mass of A are in a ratio of small whole numbers C C O OO 12 g of Carbon & 32 g of Oxygen 12 g of Carbon & 16 g of Oxygen 2 x carbon dioxide carbon monoxide

Subatomic Particles -J.J. Thompson determined charge:mass ratio of e -, Robert Millikan measured charge of e -, Thompson developed “plum pudding” model of atom -Rutherford developed “nuclear” model of atom alpha particle source detector

Modern Atomic Structure * unit charge = x C (coulomb)  amu (u) -- atomic mass unit = x g

 Atomic Number number of protons in an atom defines an element shown as the symbol subscript 6 C  Mass Number total number of protons plus neutrons will vary between isotopes shown as the symbol superscript 12 C  Isotopes elements which have the same atomic number but different mass numbers 12 C 6 13 C 6 14 C 6 are isotopes

Periodic Table –Allows for organization of elements –Allows for grouping of elements in terms of physical and chemical characteristics Metals, Non-metals & Metalloids –Group 1AAlkali Metals –Group 2AAlkaline Earth Metals –Group 6AChalcogens –Group 7AHalogens –Group 8ANobel Gases –B GroupsTransition Metals Know these !!

Molecules and Molecular Compounds Molecule — the smallest particle of a compound that can be identified as that compound — chemical combination of two or more atoms — a pure substance Chemical Formula — a symbol representation of a molecule/compound — shows the type and ratio of atoms in a molecule  type is given by symbol  ratio is given by a subscript to right of symbol

Examples: H 2 O H 2 O 2 CO 2 CO O 2 MoleculeRatio 2 : 1 2 : 2 1 : 2 1 : 1 - heteroatomic homoatomic

Formulas —Molecular Formulas Give the type and exact number of each type of atom —Empirical Formulas Give only the type and simplist ratio of atoms H2OH2O2C6H6C2H6H2OH2O2C6H6C2H6 Molecular FormulaEmpirical Formula H 2 O HO CH CH 3

— Structural Formulas Show which atoms are attached to which atoms C2H6OC2H6O H C O C H H HH H H C C O H H H H H dimethyletherethanol

Ions & Ionic Compounds Some elements will either lose or gain one or more electrons to become charged species Metals –typically lose electrons, become +, cations Non-Metals –typically gain electrons, become -, anions

Monatomic Ions –made from a single element Na  Na + + 1e - Cl + 1e -  Cl - Na Na + 1e - + Cl Cl - + 1e - 11 p + 11 e - 11 p + 10 e - 17 p + 18 e - 17 p + 17 e -

Hints to Determine Ion Charges Hydrogen +1 Oxygen- 2 Group IA +1 Group IIA +2 Group VIA- 2 Group VIIA- 1

Polyatomic Ions -- “molecules” which have a net positive or negative charge – CO 3 2- carbonate ion – NH 4 + ammonium ion – OH - hydroxide ion Prediction of Charges -- all species tend toward the most stable state – Nobel gases are very stable – Elements add or lose electrons to “mimic” nobel gases

Ionic Compounds Oppositely charged ions form ionic compounds –held together by ionic bonds due to the electrostatic attraction between the opposite charges Ionic compounds are always neutral species Mg 2+ and Cl - form MgCl 2 not MgCl or Mg 2 Cl

Naming Inorganic Compounds Names of Monatomic Ions – cations are named for the elements Na + is sodium ion Al +3 is aluminum ion Fe +2 is iron(II) ion Fe +3 is iron(III) ion (ferrous ion) (ferric ion) Cu + is copper(I) ion Cu 2+ is copper(II) ion (cuprous ion) (cupric ion) – anions are named for the root name of the element with the ending -ide O -2 is oxide ionCl - is chloride ion H - is hydride ionN -3 nitride ion

Naming Polyatomic Ions Know the names, charges and formulas of the important polyatomic ions –NH 4 + ammonium ion –CO 3 -2 carbonate ion –SO 4 -2 sulfate ion –OH - hydroxide ion –NO 3 - nitrate ion Polyatomic ions are treated as separate entities or units Naming and formula rules are the same as for compounds with monatomic ions

Naming Binary Ionic Compounds Cations always named first Anions always named last –NaCl sodium chloride –BaCl 2 barium chloride for cations which have more than one possible charge, the charge of the ion must be given in the name –Fe 2 O 3 iron(III) oxide –FeOiron(II) oxide Combinations must be neutral!

Examples: – 2 Na + and1 CO 3 -2 is sodium carbonate Na 2 CO 3 – 2 NH 4 + and 1 S -2 is ammonium sulfide (NH 4 ) 2 S – 1 Ba +2 and 2 OH - is barium hydroxide Ba(OH) 2 – 3 Mg +2 and 2 PO 4 -3 is magnesium phosphate Mg 3 (PO 4 ) 2 – 1 Na +, 1 H + and 1 CO 3 -2 is sodium hydrogen carbonate or sodium bicarbonate, NaHCO 3

Acids A compound that produces hydrogen ions (H + ) when dissolved in water tastes sour turns litmus red has a pH less than 7 typically the formula begins with one or more H’s –HCl (aq) hydrochloric acid –H 2 SO 4(aq) sulfuric acid –HC 2 H 3 O 2(aq) acetic acid

Binary Acids Acids which contain H and another non- metallic element Naming -- to the root name of the non- metallic element: –add the prefix hydro- –add suffix -ic acid HF (aq) hydrofluoric acid HBr (aq) hydrobromic acid HCl (aq) hydrochloric acid Note!

Oxyacids Acids which contain H and O and another element (or H and a polyatomic anion containing O) Naming -- to the polyatomic ion name –if the suffix is -ate, change it to -ic –if the suffix is -ite, change it to -ous –add acid to the end of the name HNO 3 nitric acid HNO 2 nitrous acid H 2 SO 4 sufuric acidH 2 SO 3 sulfurous acid You must know polyatomic ion names/charges

Binary Molecular Compounds Chemical combinations of non-metals and non- metals (no ions involved) The more metallic element is named first The second element (less metallic) is named with the ending -ide Because there are no ions to use to determine relative ratio of atoms we must indicate the number of each atom by a prefix –N 2 O 3 dinitrogen trioxide –SO 3 sulfur trioxide

Name the Following: CaI 2 Cu 2 O CuO Cl 2 O 7 HClO 3 calcium iodide copper(I) oxide copper(II) oxide dichlorine heptaoxide note chloric acid

Write Formulas for the Following: calcium hypochlorite Mg +2 and ClO 2 - carbon tetrachloride NH 4 + and SO 4 -2 Ca(ClO) 2 Mg(ClO 2 ) 2 CCl 4 (NH 4 ) 2 SO 4