Chapter 2 Atoms, Molecules, and Ions Atoms and the atomic theory Components of the atom The periodic table Molecules and Ions Ionic Formulas Names of Compounds
Atoms and the Atomic Theory Elements consist of tiny particles called atoms. Atoms retain their identity in reactions. In a compound, atoms combine in fixed ratios of small whole numbers. ( Water = 2 H, 1 O ) Key Figures: • Rutherford Discovered nucleus [Gold foil experiment] • JJ Thompson
Electrons • Thomson’s discovery of the electron • Negatively charged • Smaller than proton (1/2000) 0.005 AMU
Atomic Number = # of protons in nucleus = # of electrons in a neutral atom. (not an ion) Atomic Number is characteristic of a particular element. (all Hydrogen atoms have 1, Helium 2) Mass Number discovery of the nucleus = # of protons + # of neutrons Atomic Number, Mass Number
Isotopes of Hydrogen No neutrons 1 neutron 2 neutrons protium deuterium tritium
Nuclear stability(stable isotopes) • Small elements (Up to atomic # 20) the stable proton:neutron ratio = 1:1 • Carbon 12, C-12 is a stable carbon isotope. • C-16 is unstable. After element 20… Then more neutrons are needed to mute the repulsive force of the protons in the nucleus. • For heavy elements Atomic Number =80+ the stable P:N ratio is 1:1.5
Groups Groups Groups Non Metals periods Metals
Molecules Usually made up of non-metal atoms Held together by covalent bonds
Types of formulas Using ethyl (drinking) alcohol as an example: Molecular Formula: C2H6O Gives # and type of each element Structural Formula: Shows how atoms are bonded Condensed Structural: CH3CH2OH Gives structural hints
Ions Formation of monatomic ions Gain or lose in order to obtain a noble gas electron configuration. Lose electrons: (metals) Na Na+ + e- Gain electrons: (non-metals) F + e- F –
Cations (+) Group 1 +1 Group 2 +2 Aluminum +3 Anions (-) Group 17 -1 Group 16 -2 Nitride -3 Monatomic ion charges Find their locations on the periodic table and label them with their familiar names.
Many are polyvalent i.e. multiple possible charges. Fe2+, Fe3+ Cu+, Cu2+ Pb2+, Pb4+ Sn2+, Sn4+ Key monovalent ions: Silver Ag+ Zinc Zn2+ Monatomic ions of Transition Metalsand POST-transition metals
Polyatomic Ions • Group of several atoms acting as an ionic unit. • Ex. NO3- Nitrate • NH4+ and Hg22+ are the only common polyatomic ions with a positive charge. (Cations)
KCl NaNO3 CO2 PBr3 CoO CCl4 Ionic Ionic Molecular Molecular Ionic Molecular Determine if the following are ionic or molecular Ionic: metal and non metal (or polyatomic ion) Molecular: 2 or more non metals
Formulas of Compounds • Ionic compounds: • Apply principle of electroneutrality.
Ionic Compounds dissolved in water: “electrolytes” • Electrolytes can carry a current to complete a circuit. • Ionic compounds are electrolytes They may be strong or weak. • Molecular compounds are non-electrolytes. They will NOT carry a current to complete a circuit.
Names of compounds Ionic: • Join together the names of the 2 ions • Na+ (sodium) Br- (bromide)= NaBr = sodium bromide • Polyvalent transition metals include charge in the name • Fe3+ (Iron III) O2- (Oxide) = Fe2O3= Iron (III) Oxide • Oxo-anions • -ate, -ite, per-, hypo-
Na3N Cu(NO3)2 LiBrO2 LiF BeIO4 Sodium Nitride Copper (II) Nitrate Lithium Bromite Lithium Fluoride Beryllium Periodate Practice Naming
Names of compounds Molecular: • Use greek prefixes to indicate # of atoms • 1st element: Name + greek # if more than one. • 2nd element: Greek # prefix + “ide” version of element name. • CO2 = Carbon Dioxide
Greek Number Prefixes 1-10 • Mono • Di • Tri • Tetra • Penta • Hexa • Hepta • Octa • Nona • deca
Acids • Compounds with an “H” that ionizes in water. • HCl, in water is an electrolyte of H+ and Cl- ions. Acid naming Binary (2 types of atoms) use the “–ic” suffix
Acids • Oxo acids: • -ate salt = -ic acid NO3- is nitrate so HNO3 is Nitric Acid • -ite salt = -ous acid NO2- is nitrite so HNO2 is Nitrous Acid HClO Hypoclorous Acid HClO2 Chlorous Acid HClO3 Chloric Acid HClO4 Perchloric Acid