Download THE ATOM!

THE ATOM!
BUILDING BLOCKS OF MATTER
Rutherford!
► The
gold foil experiment
► Shot alpha particles (helium nuclei) at gold
foil
Mass number
4
2+
charge
97% of the time the alpha particle went straight through
2.7% of the time the alpha particle was deflected
0.3% of the time the alpha particle bounced back
Lead box containing alpha
particle source
Scintillation screen
Gold foil
Turn foil so you are looking at the edge. Then magnify!
Cross section of gold foil
(Magnified x1012)
Alpha particle source
Rutherford’s Results
► Most
of the atom is?
 Empty space
► In
the center of the atom is?
 Nucleus
► With
a charge of ?
 Positive (due to PROTONS, the second
particle)
The Third Particle
►Rutherford’s
co-worker
James Chadwick
discovered the NEUTRON!
►The NEUTRON has a
NEUTRAL
________charge.
If its mostly empty space
then how are things solid?
Relative Mass: Animal analogy
p+ n0
21 amu
(atomic
(atomic mass
mass unit)
unit)
1Protons and 1Neutron
Properties of Subatomic Particles
Particle
Symbol
Location
Charge
Mass (amu)
Electron
e-
Electron
Cloud
Negative
1
1840
Proton
p+
Nucleus
Positive
1
Neutron
n0
Nucleus
Neutral
1
Atomic Number
Atomic Number =
# of Protons =
# of Electrons =
Practice
Write down the symbol, NAME, atomic number, protons,
and electrons for the following.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
W
Au
U
Fr
Dy
34 p+
100 eAtomic number 11
50 p+
47 e-