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ATOM
AN ATOM IS THE SMALLEST
PARTICLE THAT HAS ALL
THE PROPERTIES OF AN
ELEMENT
GREEK ATOM
DALTON’S ATOM
Dalton's Atom Model
John Dalton (1766-1844) is the father of the chemical atomic theory. He proposed an
"atomic theory" with spherical solid atoms based upon measurable properties of mass.
The main principles of his theory: chemical elements are made of atoms; atoms of
different elements have different masses; atoms of the same element have the same
properties, such as weight.
THOMSON’S ATOM
RUTHERFORD’S EXPERIMENT
BOHR’S ATOM
Bohr's success was somewhat short lived as more careful
experiments revealed extra spectral lines which Bohr could
not account for. Sommerfield saved the day by proposing
elliptical electron orbits to explain these effects just as Kepler
had done more than three centuries earlier to explain
deviations of the orbit of Mars around the sun. Bohr's
problems were not over though. A closer look at earlier work
by Zeeman (1897) showed that extra spectral lines appeared
when excited hydrogen atoms were placed in a magnetic field.
These could be accounted for if the orientation of the orbit
was also included in the equations.
AN ATOM IS ESSENTIALLY
EMPTY SPACE
FUNDAMENTAL PARTICLES
ATOM ARRANGEMENT
Possible nucleus configuration (protons are red with + in picture)
IN THEIR NORMAL STATE
ATOMS ARE NEUTRAL
# PROTONS
# ELECTRONS
ATOM SHELLS
K
L
M
MAXIMUM ELECTRONS PER
SHELL
2n2
n-SHELL #
K-2
L-8
M-18
N-32
O-50
MAX. # OF ELECTRONS ON
SHELLS
Electron shells for a Sodium atom
(atomic number 11, with 11 electrons)
2n2
CENTRIPETAL FORCE vs
CENTRIFUGAL FORCE
ELECTRON BINDING ENERGY
BINDING ENERGY
ELECTRON BINDING ENERGY
BINDING ENERGIES
TUNGSTEN
TUNGSTEN-74
BINDING ENERGIES
OF DIFFERENT SHELL ELECTRONS
K-70 KEV
L-12 KEV
M-2.8 KEV
BARIUM-56
BINDING ENERGIES
OF DIFFERENT SHELL ELECTRONS
K-37 KEV
L-6 KEV
M-1.3 KEV
IONIZATION
IF ENERGY OF INCOMING
PARTICLE/PHOTON>BINDING ENERGY
OF THE ELECTRON
EXCITATION
IF ENERGY OF INCOMING
PARTICLE/PHOTON<BINDING ENERGY
OF THE ELECTRON
OUTER SHELL IONIZATION
INNER SHELL IONIZATION
CASCADE!
PERIODIC TABLE
Z
A
8 MAXIMUM # OF
ELECTRONS ON THE LAST
SHELL --- VALENCE SHELL
8
CHEMICAL BONDS
BONDS
BONDS
BONDS
BONDS
ISOTOPES
ISOBARS
ISOTONES
A#-Z#= SAME
ISOMERS