Chapter 2Atoms, Molecules and IonsA. Chemical Elements and CompoundsB. Atomic ParticlesC. IsotopesD. Atomic Mass and Molecular MassE. NomenclatureHW #P1P1 is covered on Q1 and T1Chapter 2A. Chemical Elements and Periodic TableChemical Elements  90 naturally occurringEverything is composed of these elements.Elements combine to form compounds.If one divides an element to the smallest unit, which retains identity  atomAtoms combine to form molecules.H + H + OH HOwatermacroscopic scale atomic scaleelements atomscompounds molecules (Fig 2.17)B. Atomic Particles, Nuclear AtomEach atom is composed of particles.Particle Charge Massproton + 1.67 × 10-24 gneutron none 1.67 × 10-24 gelectron - 9.11 × 10-28 gProtons and neutrons are the nucleus. Atom diameter is Å; nucleus is 10-4ÅMass is in nucleus  nuclear density is 1013 g/cm3.The number of protons gives the Atomic Number. The number of neutrons gives the Isotope. All chemical changes are electronic involving a changein the electrons (nuclear chemistry is the exception!)C. Isotopes and Atomic WeightAtomic number (the # of protons) specifies the atom. 12CAtomic number = 6Atomic mass = 126How many neutrons?How many electrons?Examples:1.55MnHow many protons,neutrons, electrons?252.55Mn2+How many protons, neutrons,electrons?253. a) How are 35Cl and 37Cl different?b) If 35Cl is present in 75.5% and 37Cl is present in 24.5%, what would atomic mass be for a natural mixture of Cl atoms? – This Is Atomic Weight.D. Atomic Mass and Molecular MassAtomic mass is obtained from periodic table or other source.H = 1.008C = 12.01O = 16.00Molecular mass is the sum of atomic masses whichmake up the molecule.Examples:1. H2O2. CO2E. Nomenclature (read 62-69) (Not Acids or Organic Compounds)1. Ionic CompoundsCation then anionNaCl[Na+] [Cl-]Sodium chloride Simple metal cations are just the element name, perhaps with the oxidation state. Anions are indicated by “ide” ending.Based on atomsTables 2.4, 2.5Atoms which gain electrons are negatively charged and called anions.Cl + 1e-  Cl- chlorideAtoms which lose electrons are positively charged and called cations.Na - 1e-  Na+Ionic compounds are formed when the negative and positive charges are balanced (add to zero).Na+ + Cl-  NaClNeed to learn common cations and anions:Cations – Table 2.4Anions – Table 2.5Some common anions: remember for quizzesCO32-carbonateNO3-nitratePO43-phosphate SO42-sulfateClO4-perchlorateOH-hydroxide2. Binary Molecular CompoundsGreek prefixes indicate the number of atoms.CO Carbon monoxideCO2Carbon dioxideN2O4Dinitrogen