CHEM 111 1st Edition Lecture 2Classification of MatterAll substances are made of atomsAtoms are made of protons, electrons, and neutrons# of protons in an atom determines what chemical element it is# of protons is the atomic numberMass number is the number of neutrons and protons(Mass Number)(Atomic Number)Isotopes have different naturally occurring abundances in nature, so atomic weights (atomic masses) are weighted averages over natural abundancesAtomic weight of Carbon 12 is 12.0 uBut the atomic weight of Carbon is 12.01 u (see periodic table)Covalent and Ionic Bonding: Two ways that atoms can bond and form compoundsCovalent: Sharing electrons especially between non-metalsIonic: Electrons transfer, then opposite charges attractCoulomb’s Law F=q 1× q 2r2Where F=forceq1xq2=charger^2=inter-nuclear distanceMolecular Compounds have several chemical formulas:Empirical (least information)MolecularCondensed StructuralStructural (most information)Ionic compounds (and network solids) have ONLY an empirical formula derived from the elemental percentage compositionsEx. NaCl “molecules” are not found in natureEmpirical- Smallest whole number ratios of atomsEx. CH2O (could be glucose or formaldehyde)Structural-shows how everything is connected H HThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. HeH C O C H H HMolecular-shows actual number of each atom in a moleculeEx. Glucose: C6H12O6Condensed Structural-shows common functional groups and indicates structureCH3OCH3 (see
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