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Nuclear Chemistry
The Atom
The atom consists of two parts:
1. The nucleus which contains:
2. Orbiting electrons.
protonsneutrons
XA
Z
Mass number
Atomic number
Element symbol
= number of protons + number of neutrons
= number of protons
U235
92U
238
92
There are many types of uranium:
Mass #
Atomic #
Number of protons
Number of neutrons
Mass #
Atomic #
Number of protons
Number of neutrons
235
92
92
143 146
92
92
238
Same number of protons but different number of neutrons is
an…..
ISOTOPE
Most naturally occurring isotopes are stable.
Atoms want to be stable
Determined by ratio of p+ to n0
Nucleus Stability
Radioactive Decay(radioactivity)
Unstable nuclei decomposes into stable nuclei
Half- Life is the time it takes for this decay to occur.
Click Link to View Video:https://www.dropbox.com/s/0c380hppk60ikz1/Nuclear%20Half%20Life_%20Calculations.mp4?dl=0
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 Iodine -131 left after 40.35 days. How many grams were in the original sample if its half-life is 8.07 days?
• an alpha particle (a),
• a beta particle (b),
• or a gamma ray( ).g
Radioactive Decay emits:
When an unstable atom creates an alpha particle.
Alpha particle is identical to that of a helium nucleus. It contains two protons and two neutrons.
Alpha Decay
He4
2
Alpha Decay
Ra226
88
Rn222
86
He4
2
XA
ZY
A - 4
Z - 2+ He
4
2
Alpha Decay
unstable atom
more stable atom
alpha particle
Alpha Decay
Ra226
88+ He
4
2Th
230
90
U234
92Th
230
90+ He
4
2
+Pb214
82He
4
2Po
218
84
Beta Decay
Beta particle is a fast moving electron created when a n0 changes into a p+ & e-
When an unstable atom creates a beta particle.
Beta Decay
Po218
84
b0
-1
At218
85
XA
ZY
A
Z + 1+ b
0
-1
Beta Decay
unstable atom
more stable atom
beta particle
Beta Decay
Bi210
83 Po210
84+ b
0
-1
Pb210
82Tl210
81+ b
0
-1
Pa234
91Th
234
90+ b
0
-1
Gamma Decay
• Not a charged particle it is energy, it’s a photon.
• Electromagnetic radiation with high frequency
Draw the correct wave
Symbol Composition Range ShieldAlpha Particle
He or α
Helium nucleus
Beta Particle Gamma Ray
short Paper, skin
Symbol Composition Range ShieldAlpha Particle
He or α
Helium nucleus
Beta Particle
e- or β
Electron
Gamma Ray
short Paper, skin
Heavy Clothing, glass, light metals, plastic
Symbol Composition Range ShieldAlpha Particle
He or α
Heliumnucleus
Beta Particle
e- or β
Electron
Gamma Ray
Photons (electromagnetic spectrum)
short Paper, skin
Heavy Clothing, glass, light metals, plastic
Long Lead or concrete