CHEM 400 Exam 1

Week 1 Main Concepts

Early Atomic Theory

  • 1807 - John Dalton aka “Father of Modern Atomic Theory”

  1. All matter is made up of atoms. Atoms are the smallest particle that retain the identity of an element.

  2. Element consists of only one type of atoms.

  3. Atoms of one element differ from atoms of all other elements.

  4. Compound is made up of 2 or more types of atoms combined in small, whole number ratios.

  5. Atoms are neither created nor destroyed, but rearranged. Conservation of mass.

  • Law of Definite Proportions: same compound always has the same composition

  • Law of Multiple Proportions: same elements can combine in different ratios to make up different compounds

Modern Atomic Discoveries

  • J.J. Thomson discovered electrons.

  • Robert Millikan obtained the charge of electrons

  • Rutherford’s gold foil experiment

    • Atoms are mostly empty space

    • Nucleus is small, very heavy, and positively charged

  • James Chadwick discovered neutrons

  • A = mass number, sum of protons and neutrons

  • Z = atomic number, number of protons

  • AzSy - standard isotopic notation

  • Isotopes: atoms of the same element with different number of neutrons

  • Average mass of an element is calculated by averaging all the masses of the isotopes and weighing them by their relative percent abundance in the universe.

Periodic Table

  • Metals v. nonmetals

  • Main group elements v. transition elements

  • Families are the vertical columns

    • Family 1 - Alkali

    • Family 2 - Alkali earth metals

    • Family 15 - Pnictogens

    • Family 16 - Chalcogens

    • Family 17 - Halogens

    • Family 18 - Noble gases

    • Lanthanides and actinides

Nomenclature of Ionic Compounds

  • Metal first, nonmetal second

  • Positive ion first, negative ion second

  • The sum of all charges on all ions must be zero

  • Parentheses are used when a polyatomic ion is needed more than once

Nomenclature of Molecular Compounds

  • Nonmetal followed by a nonmetal

  • Use prefixes to indicate the number of atoms present in the compound.

    • Mono = one

    • Di = two

    • Tri = three

    • Tetra = four

    • Penta = five

    • Hexa = six

    • Hepta = seven

    • Octa = eight

    • Nona = nine

    • Deca = ten

Week 2 Main Concepts

Nomenclature

  • Ionic Compounds

    • Metal + nonmetal

    • Cation + anion

    • Naming ionic compounds

      • Binary - have only two types of atoms

      • Ternary - contain a polyatomic ion

      • All charges must add up to zero

  • Molecular compounds

    • All nonmetals

  • Naming Binary Molecular compounds

    • First element + second element ending in -ide

    • Use prefixes: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

Moles

  • NA = 6.022 Ă— 1023 = Avogadro’s number

  • Molar mass = mass of 1 mole of particles

  • Periodic table always reports mass of one moles of atoms

  • Formula mass is the sum of all masses making up the formula

  • Converting between grams, moles, number of formula units, number of specific atoms if a formula is given.

  • % composition

Week 3 Main Concepts

Moles

  • NA = 6.022 Ă— 1023

  • Molar mass = mass of 1 mole of particles

  • Periodic table always reports mass of one moles of atoms

  • Formula mass is the sum of all masses making up the formula

  • Converting between grams, moles, number of formula units, number of specific atoms if a formula is given.

  • % composition

  • Empirical/molecular formula

  • Molarity = mol/L

Stoichiometry

  • Molar relationships between different substances in a balanced equation.

  • Mole-mole stoichiometry problems

  • Mole-mass stoichiometry problems

  • Mass-mass stoichiometry problems

  • Limiting reagent problems

  • Actual yield: the amount of product that is realistically made in a lab setting

  • Theoretical yield: the amount of product that can be calculated on paper

  • Percent yield: (Actual/Theoretical) x 100%

Double Replacement Reactions

  • AX + BY —> AY + BX

    • Acid base neutralization reactions are double replacement reactions.

    • Precipitation reactions are double replacement reactions.

    • Solubility rules

Chemistry History

  • John Dalton aka “Father of Modern Atomic Theory”

    • All matter is made up of atoms. Atoms are the smallest particle that retain the identity of an element.

    • Element consists of only one type of atoms.

    • Atoms of one element differ from atoms of all other elements.

    • Compound is made up of 2 or more types of atoms combined in small, whole number ratios.

    • Atoms are neither created nor destroyed, but rearranged. Conservation of mass.

    • Law of Definite Proportions: same compound always has the same composition

    • Law of Multiple Proportions: same elements can combine in different ratios to make up different compounds

  • Robert Millikan obtained the charge of electrons through the Oil Drop Experiment.

  • Rutherford’s Gold Foil Experiment: discovers nucleus and protons

    • Alpha particles through gold foil.

      • Most alpha particles travel through the foil undetected

        • Atoms are mostly empty space

      • Some alpha particles are deflected by small angles

        • Nucleus is small, very heavy, and positively charged

      • Occasionally, an alpha particle travels back from the foil

        • The nucleus carries most of the atom’s mass

  • James Chadwick discovered neutrons.

  • J.J. Thomson discovered electrons.