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Atoms and the Periodic Table Chapter 8 Homework Assignment Chap 8 Read p 223 – 231; 236 - 242 Applying the Concepts (p 243): 1 – 13, 15 – 17, 19, 23 - 35, 39 – 44, 46 - 50 Dalton’s Atomic Theory (1808) (Listed on p 224) 1. Elements are composed of extremely small particles called atoms. 2. All atoms of a given element are identical, having the same size, mass and chemical properties. 3. The atoms of one element are different from the atoms of all other elements. 4. Compounds are composed of atoms of more than one element. The relative number of atoms of each element in a given compound is always the same. 5. Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed in chemical reactions. Particles in an atom Cathode Ray Tube Fig 8.2 J.J. Thomson, discovered the electron (1906 Nobel Prize in Physics) N S (1908 Nobel Prize in Chemistry) Fig 8.5 Fig 8.6 1. Atom’s positive charge is concentrated in the nucleus 2. Proton (p) has opposite (+) charge of electron (-) Planetary Model of the Atom Empty space! atomic radius ~ 1 x 10-10 m nuclear radius ~ 5 x 10-15 m “If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.” Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons Isotopes - atoms of the same element (X) with different numbers of neutrons in their nuclei Mass Number A ZX Atomic Number 1 1H 235 92 2 1H U Element Symbol (D) 238 92 0.72% natural abundance 3 1H U (T) Do You Understand Isotopes? How many protons, neutrons, and electrons are 14 in 6 C ? 6 protons, 8 (14 - 6) neutrons, 6 electrons How many protons, neutrons, and electrons are 84 in 38 Sr ? 38 protons, 46 (84 - 38) neutrons, 38 electrons Visible light consists of electromagnetic waves Fig. 7.2 Electromagnetic radiation: emission and transmission of energy in the form of electromagnetic waves. Speed of light (c) in vacuum = 3.00 x 108 m/s Fig. 7.3 The Electromagnetic Spectrum White light is separated into its color components by a prism White light is separated into its color components by a diffraction grating The tracks of a compact disc act as a diffraction grating, producing a separation of the colors of white light. Fig 8.8 Atomic Emission Spectra Line Emission Spectrum of Hydrogen Atoms 7.3 First recorded emission spectrum of the sun (1817) intensity wavelength Bohr’s Model of the Atom (1913) 1. e- can only have specific (quantized) energy values 2. light is emitted as emoves from one energy level to a lower energy level n (principal quantum number) = 1,2,3,… Fig 8.10 e- E = hn Fig 9.18 E = hn Egreen > Ered High energy Low energy Electron configurations of some atoms Valence electrons ≡ electrons in outermost shell Fig 2.9 Physical Properties of the Elements Metals • good conductors of heat and electricity • shiny, ductile, malleable • all solids with one exception Nonmetals • poor conductors • dull appearance, brittle • consist of solids, liquids, and gases p 237 Noble Gas Halogen Group Alkali Metal Alkali Earth Metal Period Chemistry In Action Natural abundance of elements in Earth’s crust Natural abundance of elements in human body