Transcript Radioactivity

Unit 17
Radioactivity
Atomic mass is the
average number of p+ and
n found in the nucleus.
Carbon
12.0111
6
C
All elements have Isotopes.
Atoms of the same element
with a different number of
neutrons found in the
nucleus, therefore they
have different masses.
Chemical symbol: 1 or 2 letters
used to represent an element.
The 1st letter is always capital.
If there is a 2nd letter, it is
lower case.
Atomic number is the
number of p+ found in the
nucleus.
Subatomic Particles
Particle
Mass
Charge
Location in
the atom
Proton (p+)
1 amu
+1
Nucleus
1.673 x 10-24 g
1.602 x 10-19 C
1 amu
0
Nucleus
-1
Revolving
around
nucleus
Neutron
(n)
Electron
(e-)
(center of atom)
1.675 x 10-24 g
1/
1837
amu
9.109 x 10-28 g
-1.602 x 10-19 C
Structure of the Atom
Protons & Neutrons
Radioactivity
1.
2.
3.
All naturally occurring elements with atomic
numbers greater than 83 are radioactive. Uranium
is the largest naturally occurring element. Every
element above 92 is man-made.
Radioactivity is the uncontrollable decay of an
atomic nucleus with the emission of particles and
rays, with a lighter element formed.
Radioactive elements can affect photographic
plates, ionize gases, and cause physical effects
(mutations).
4.
Half-life is the TIME it takes for ½ of the
radioactive atoms to decay.
Different elements take a different amount of time
for a half-life to occur.
U  Th
half-life takes 4.5 billion years
Po  Pb
half-life takes 1.6 x 10-4 seconds
Remember that half-life is the period of time required
for half of the atoms to go through decay.
For a single element, each half – life is the same amount
of time.
So, if it takes 2 minutes for element X to go through
one half – life, it takes 4 minutes to go through 2
half – lives.
During each half – life, half of the atoms go through
decay.
remaining
1g
½g
1st half-life
decayed
½g
¼g
2nd
1/
8
g
3rd
¾g
7/
8
g
Radioactive Emissions



Alpha particle a = Helium nucle
easily stopped
Beta particle b = electron emoderately difficult to stop
Gamma ray g = pure energy
very difficult to stop
4
2
He
Radioactive emission
causes ionization of Ar gas,
completing circuit, clicks!
How a Geiger Counter works
a or b
Typical nuclear reactor
Drawing of
the
condition
of
Chernobyl
reactor
after the
melt down
Chernobyl
reactor
after the
melt down
Chernobyl reactor core
New structure that will
enclose the destroyed
reactor at Chernobyl.
500 feet long, 840 feet wide,
and taller than the Statue of
Liberty.
Fukushima
Daiichi
Power Plant
Japan
Nuclear Notation
Atomic mass
A
z
Atomic number
X
Element symbol
Kinds of Decay
Alpha decay a
A
Z
a
X 
A-4
Z-2
N + 24 He
N = new element
Beta decay b
A
Z
b
X 
A
Z+1
N + e-
N  p+ + e-
a
b
241Pu
94
a
b
a
a
b
Bikini island
Review
a
1.
a.
226Ra

88
a
222Rn
86
b
b.
214Bi
83
2.
3.
4.
5.


218Po
84
b
214Po
84

214At
85
Protons and neutrons are located in the nucleus, with the electrons located
in energy levels around the nucleus.
Alpha a particle is a helium nucleus
Beta b particle is an electron
Gamma g ray is pure energy
1/8 pound remaining
7/8 pound decayed
A device used to detect radiation by counting the number of emissions
per unit of time
Nuclear chemistry Crossword
Down
27. Cyclotron
28. Spectrograph
39. Meson
Across
16. Emanations
18. Crystallization
34. Becquerel
40. Rutherford
45. Electroscope
Size:
468 × 454
Type:
39KB JPG
Mushroom
Cloud
from a
nuclear
bomb.
Bikini Atoll is a circle of island with a deep central lagoon.From 1946 to 1958
the US exploded 23 nuclear bombs to analyze what happens. All of the local
people were relocated to another atoll before the explosions
Light Bright Assignment
1H
2H
3H
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..
...
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