Transcript Nuclear Reactions

NUCLEAR REACTIONS
NUCLEAR FUSION
• Nuclei forced together to form heavier
nuclei.
• Needs extremely high temperatures
(15,000,000 °C) to happen.
• Large amounts of energy are released
• How the sun releases its energy
• Hydrogen Bomb – nuclear weapons
NUCLEAR FUSION
NUCLEAR FISSION
• An atom's nucleus (parent atom) splits
into two or more smaller nuclei
(daughter atom).
• Exothermic process.
• Releases energy and gamma radiation.
• Atomic Bomb – “Little Boy” and “Fat
Man” on Japan
FISSION
3 MAIN TYPES OF RADIOACTIVE DECAY
• Alpha
a
• Beta
b
• Gamma g
WHY NUCLEAR DECAY?
• So it becomes more stable.
• The atom will decay until it becomes like
Lead - Atomic #82
• Nuclei with atomic number > 83 are
radioactive
RADIOACTIVITY
• Process where an atom gives off
particles of radiation by the
spontaneous decay of the nucleus.
RADIOACTIVE
• Radioactive – any material that
spontaneously gives off particles
of radiation (alpha, beta, gamma)
NUCLEAR RADIATION
• The particles given off during reactions
that involve the nucleus of an atom.
ALPHA DECAY
Alpha particle (a) :
• Has 2 protons and 2 neutrons
• It is a Helium nucleus
• Mass is four = 2 protons plus 2 neutrons
• Can travel a few inches through air
• Can be stopped by a sheet of paper
or clothing.
ALPHA DECAY
• When an atom gives off an alpha particle,
the mass number decreases by four due to
the loss of the 4 nucleons (2 protons and 2
neutrons).
• The atomic number of the atom goes down
by two, because it has lost two protons.
• The atom becomes a new element.
ALPHA DECAY
Uranium
Thorium
+ Alpha Particle
BETA DECAY
• A high speed electron leaves the
nucleus.
• Beta Decay occurs in elements with
more neutrons than protons.
BETA DECAY
• A neutron splits into a proton and an
electron.
• The proton stays in the nucleus.
• The electron is released – the mass of the
parent atom stays the same.
BETA DECAY
• Beta particles have the same charge
and mass as "normal" electrons.
Beta Particle
BETA DECAY
Thorium
Protactinium
+ Beta particle
GAMMA RADIATION
• Gamma radiation g : electromagnetic
energy that is released.
• Gamma rays are electromagnetic
waves.
• They have no mass.
• Gamma radiation has no charge.
• Most Penetrating, can be stopped by
1m thick concrete or a several cm
thick sheet of lead.
RADIOACTIVE HALF-LIFE
• The time it takes for half of the
radioactive nuclei in a given
sample to decay.
AMOUNT OF REMAINING NUCLEI VS
TIME
HALF-LIFE EXAMPLE
• You have 100 g of radioactive C-14.
• The half-life of C-14 is 5730 years.
• How many grams are left after one
half-life?
• How many grams are left after
2 half-lives?
HALF-LIFE EXAMPLES
A sample of 100,000,000 Radon atoms are trapped
in a basement that is sealed. The half-life of
Radon is 3.83 days.
How many radon atoms are left after 30 days?
ANSWER
½ Life #
Days Gone
Sample Size
0
0
100000000
1
3.83
50000000
2
7.66
25000000
3
11.49
12500000
4
15.32
6250000
5
19.15
3125000
6
22.98
1562500
7
26.81
781250
8
30.64
390625