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Atoms and the Periodic
Table
Chapter 8
Homework Assignment
Chap 8
Read p 203 – 211; 216 - 222
Applying the Concepts (p 222): 1 – 13,
15 – 17, 19, 23 - 35, 39 – 43, 45 - 49
Dalton’s Atomic Theory (1808)
(Listed on p 203)
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.”
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 8.17 Periodic Table of the Elements
Development of Periodic Table
Dmitri
Mendeleev and
Lothar Meyer
independently
came to the
same conclusion
about how
elements should
be grouped.
Periodic
Properties
of the
Elements
© 2009, Prentice-Hall, Inc.
Physical Properties of the Elements
Metals
• good conductors of heat
•and electricity
• shiny, ductile, malleable
• all solids with one exception
Physical Properties of the Elements
Nonmetals
• poor conductors
• dull appearance, brittle
• consist of solids, liquids,
and gases
Physical 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
Fig 8.17 Periodic Table of the Elements
Noble Gas
Halogen
Group
Alkali Earth Metal
Alkali Metal
Period
Alkali Metals – Group 1A
• Alkali metals are soft solids
• Never found free in nature
• All react violently with water:
Periodic
Properties
of the
Elements

Soft solids but harder than
alkali metals

Never found free in nature

All react slowly with water to
form bases:
THE HALOGENS – GROUP 7A
bomine

Typical nonmetals

The name comes from the Greek
words meaning “salt formers”
chlorine
iodine
Periodic
Properties
of the
Elements
• All very unreactive
• Exist as atoms
Electron dot notation for the representative elements
Fig 8.18
Show only valence electrons!
Chemistry In Action
Natural abundance of elements in Earth’s crust
Natural abundance of elements in human body