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Atoms and the Periodic Atoms and the Periodic TableTable
Chapter 8Chapter 8
Homework AssignmentHomework AssignmentChap 8Chap 8
Read p 203 – 211; 216 - 222Read p 203 – 211; 216 - 222
Applying the Concepts (p 222): 1 – 13, Applying the Concepts (p 222): 1 – 13,
15 – 17, 19, 23 - 35, 39 – 43, 45 - 4915 – 17, 19, 23 - 35, 39 – 43, 45 - 49
Dalton’s Atomic Theory (1808)Dalton’s Atomic Theory (1808)(Listed on p 203)(Listed on p 203)
1.1. ElementsElements are composed of extremely small particles are composed of extremely small particles called called atomsatoms. .
2.2. All atoms of a given element are identical, having the All atoms of a given element are identical, having the same size, mass and chemical properties. same size, mass and chemical properties.
3.3. The atoms of one element are different from the atoms of The atoms of one element are different from the atoms of all other elements.all other elements.
4. 4. CompoundsCompounds are composed of atoms of more than one are composed of atoms of more than one element. The relative number of atoms of each element in element. The relative number of atoms of each element in a given compound is always the same.a given compound is always the same.
5. Chemical reactions only involve the rearrangement of atoms. 5. Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed in chemical reactions. Atoms are not created or destroyed in chemical reactions.
Particles in an atom
Cathode Ray Tube
N S
J.J. Thomson, discovered the electron
(1906 Nobel Prize in Physics)
Fig 8.2
1. Atom’s positive charge is concentrated in the nucleus2. Proton (p) has opposite (+) charge of electron (-)
(1908 Nobel Prize in Chemistry)
Fig 8.5 Fig 8.6
atomic radius ~ 1 x 10-10 m
nuclear radius ~ 5 x 10-15 m
Planetary Model of the Atom
“If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.”
Empty space!
6 protons, 8 (14 - 6) neutrons, 6 electrons
38 protons, 46 (84 - 38) neutrons, 38 electrons
Do You Understand Isotopes?
How many protons, neutrons, and electrons are in C14
6 ?
How many protons, neutrons, and electrons are in Sr 84
38 ?
Visible light consists of electromagnetic waves
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. 7.2
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.
Line Emission Spectrum of Hydrogen Atoms
Fig 8.8 Atomic Emission Spectra
7.3
First recorded emission spectrum of the sun (1817)
intensity
wavelength
1. e- can only have specific (quantized) energy values
2. light is emitted as e- moves from one energy level to a lower energy level
Bohr’s Model of the Atom (1913)
n (principal quantum number) = 1,2,3,…
Fig 8.10
e-
E = h
E = h
Low energyHigh energy
Egreen > Ered
Fig 9.18
Electron configurations of some atoms
Valence electrons ≡ electrons in outermost shell
Fig 8.17 Periodic Table of the Elements
PeriodicProperties
of the Elements
© 2009, Prentice-Hall, Inc.
Development of Periodic Table
Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped.
Metals
• good conductors of heat•and electricity
• shiny, ductile, malleable
• all solids with one exception
Physical Properties of the ElementsPhysical Properties of the Elements
Nonmetals
• poor conductors
• dull appearance, brittle
• consist of solids, liquids, and gases
Physical Properties of the ElementsPhysical Properties of the Elements
Metalloids
• Have some characteristics of metals and some of nonmetals
• For instance, silicon looks shiny, but is brittle and fairly poor conductor
Physical Properties of the ElementsPhysical Properties of the Elements
Period
Group
Alkali M
etal
Noble G
as
Halogen
Alkali E
arth Metal
Fig 8.17 Periodic Table of the Elements
PeriodicProperties
of the Elements
Alkali Metals – Group 1A
• Alkali metals are soft solids
• Never found free in nature
• All react violently with water:
Soft solids but harder than alkali metals
Never found free in nature
All react slowly with water toform bases:
PeriodicProperties
of the Elements
THE HALOGENS – GROUP 7A
Typical nonmetals
The name comes from the Greek words meaning “salt formers”
iodine
chlorine
bomine
• All very unreactive
• Exist as atoms
Fig 8.18
Show only valence electrons!
Electron dot notation for the representative elements
Chemistry In ActionNatural abundance of elements in Earth’s crust
Natural abundance of elements in human body