Transcript Nuclear Chemistry

Nuclear Chemistry
The Atom = Nuclide
The atom consists of two parts:
1. The nucleus which contains:
protons
neutrons
Multiple nuclei is
called nucleons
2. Orbiting electrons.
Mass number = number of protons + number of neutrons
A
X
Z
Atomic number = number of protons
Element symbol
There are many types of uranium:
235
238
U
92
U
92
Mass #
235
Mass #
238
Atomic #
92
Atomic #
92
Number of protons
92
Number of protons
92
Number of neutrons
143
Number of neutrons
146
Same number of protons but different
number of neutrons is a…..
ISOTOPE
Most naturally occurring isotopes are stable.
Atoms want to be stable
Ratio of p+ to n0 determines….
Nucleus Stability
Unstable nuclei decomposes into stable nuclei, this is called…
Radioactive Decay
(radioactivity)
Radioactive Decay emits:
• an alpha particle (a),
• a beta particle (b),
• or a gamma ray(g).
Alpha Decay
An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.
4
He
2
Alpha Decay
222
226
Ra
88
Rn
86
4
He
2
Alpha Decay
A
X
Z
A-4
4
Y
He
+
Z-2
2
unstable atom
alpha particle
more stable atom
Alpha
Decay
234
U
92
230
Th
90
226
Ra
88
230
4
Th
He
+
90
2
226
4
Ra
He
+
88
2
222
Rn
+
86
4
He
2
Alpha Decay
222
Rn
86
218
Po
84
218
Po
+
84
214
4
He
2
4
Pb
He
+
82
2
Symbol
Alpha
Particle
Beta
Particle
Gamma
Ray
Composition Range
He Helium
short
or α
Shield
Paper, skin
Beta Decay is a fast moving electron.
Created when a n0 changes into a p+ & e-
Beta Decay
218
218
Po
84
At
85
b
-1
0
Beta Decay
A
X
Z
A
Y
+
Z+1
unstable atom
b
-1
0
beta particle
more stable atom
Beta Decay
218
218
b
-1
234
234
b
-1
Po
84
Th
90
Rn
+
85
Pa
+
91
0
0
Beta Decay
210
210
b
-1
214
214
b
-1
210
210
b
-1
Tl
81
Pb
82
Bi
83
Pb
+
82
Bi
+
83
Po
+
84
0
0
0
Symbol
Alpha
Particle
Beta
Particle
Gamma
Ray
Composition Range
He Helium
short
or α
e- Electron
or β
Shield
Paper, skin
Heavy Clothing, glass,
light metals, plastic
Gamma Decay
• Not a charged particle it is energy.
• Electromagnetic radiation with high frequency
Draw the correct wave
Symbol
Alpha
Particle
Beta
Particle
Gamma
Ray
Composition Range
He Helium
short
or α
e- Electron
or β
g Photons
Long
(electromagnetic
spectrum)
Shield
Paper, skin
Heavy Clothing, glass,
light metals, plastic
Lead or concrete
Half Life: Time for half of the radioactive nuclide to decay
1. How much of a 100 g sample of 198Au is left over 8.10
days if its half-life is 2.70 days?
2. A 50.0 g sample of 16N decays to 12.5 g in
14.4 seconds. What is the half-life?
3. The half life of 42K is 12.4 hours. How much
of a 750g sample is left over after 62.0 hours?
4. What is the half-life of 99Tc if a 500 g
sample decays to 62.5g in 639, 000 years?
5. There are 5.0 g of 131I left after 40.35 days.
How many grams were in the original sample if its
half-life is 8.07 days?