I. The Periodic Table A. Chart giving data about the known elements

1. I. The Periodic Table • A. Chart giving data about the known elements

2. History • Dmitri Mendeleev given credit for an early version of periodic table • In 1869 • Recognized recurring pattern of element properties with mass increase • Discovery of Elements in the Periodic Table

3. C. Information on a Periodic Table • Name and/or Symbol for each element • a. Most elemental symbols are abbreviations of their name • b. Some symbols come from older names for the element • i. Fe for Iron comes from the older name Ferrum • ii. Au for Gold come from the older name Aurum • Atomic Number = number of protons in the element (electrons if neutral) • General Properties • Metal (copper) • Conductive, malleable, ductile, and lustrous • Lose electrons to form cations • Nonmetal (oxygen) • Lack the metallic properties • Gain electrons to become anions • Groups or Families are arranged in columns • Similar reactivities • Group I = Alkali metals = reactive and easily form +1 cations • Group VIII = Noble Gases = unreactive gases

4. 5. Main Group and Transition Elements • Families or Groups on the Periodic Table • Group 1A = Alkali Metals—reactive metals • Group 2A = Alkaline Earth Metals—fairly reactive metals • Group 7A = Halogens—very reactive nonmetals • Group 8A = Noble Gases—almost completely unreactive

5. 7. Ions and the Periodic Table • Main Group Metals tend to lose electrons and form cations • Main Group Nonmetals tend to gain electrons and form anions • Group 1A forms +1 cations • Group 2A forms +2 cations • Group 3A metal (Aluminum) forms +3 cation • Group 5A (Nitrogen) form -3 anion • Group 6A nonmetals form -2 anions • Group 7A nonmetals form -1 anions Achieve Noble Gas Electron #’s

6. II. Atomic Masses • Mass spectrometers and atomic masses • Carbon is used as the standard for atomic masses • In 1961, 12C was assigned a mass of exactly 12 atomic mass units (amu) • A mass spectrometer can compare other elements or isotopes to 12C • 13C is found to be 1.0836129 times as massive as 12C • Mass of 13C = (1.0836129)(12 amu) = 13.003355 amu

7. Average Atomic Masses • Why isn’t the mass of Carbon listed at exactly 12 on the periodic table? • Natural carbon: 12C(98.89%), 13C(1.11%), and 14C (negligible) • Avg. Mass = (0.9889)(12 amu) + (0.0111)(13.0034 amu) = 12.01 amu • No individual atoms have this mass • On average, all natural carbon atoms have this mass • 12.01 amu is the correct value to use for calculations involving carbon • Example: What is avg. mass of Cu? • 69.17% 63Cu (62.9396 amu) and 30.83% 65Cu (64.9278 amu) • Calculate the Mass (in amu) of 75 atoms of Al • a. Determine the mass of 1 Al atom: 1 atom of Al = 26.98 amu • b. Use the relationship as a conversion factor 69.17 30.83

8. III. The Mole • We use a package for atoms and molecules called a mole • A mole = • a. the number of Carbon atoms in 12 g of 12C • 6.022 x 1023 units = Avogadro’s Number • The amount of an element equal to its atomic mass • 1 mole of natural C atoms weighs 12.01 g and has 6.02 x 1023 atoms • 1 mole of He atoms weighs 4.003 g and has 6.02 x 1023 atoms • 1 mole of Al atoms weighs 26.98 g and has 6.02 x 1023 atoms • Example: What is the mass of 6 Americium atoms? • Calculating moles, mass, and atoms • 1. Example: # atom / moles in 10g Al Cu I2 Hg Al Fe S

9. C. A mole is the chemists “dozen” • A dozen marbles and a dozen peas both have 12 • A dozen marbles might weigh 100 grams • A dozen peas might weigh only 15 grams • 4. Example: 5.68 mg Si = ? atoms Si