1. 7.2 & 7.3 Nuclear Chemistry
Radioactivity, Isotopes, Half-Life, Fission and Fusion.

2. Isotopes
 Isotopes are atoms of the same element
(same number of protons) that have
different number of neutrons = different
atomic mass, same atomic number.
 Changing one element to another or one
isotope to another is called Transmutation

3. Radiation
 Radioactivity (aka
Radioactive decay) is
decomposition of a nucleus
to form a different nucleus.
 It is the release of high-
energy particles and rays of
energy which change the
nucleus.
 Radioactivity occurs
because of isotopes wanting
to become stable.

4. 7.2 Half Life
 The time it takes for exactly one-half of a
radio active sample to decay.
 The shorter the half life the faster the decay.
 The half-life for a given isotope is always the
same.
 Using the half-life scientists can calculate
how much of a sample will be gone in a
given amount of time.

5. Half life continued.
 For example Strontium-90
starts with 10 g, after it’s first
half-life (29 years) it becomes
5 g, second half-life (58
years) is 25 g, and so on.
 A decay curve is a curved
line on a graph that shows
the rate at which the sample
it is decaying. (x= number of
half lives, y axis = how much
remaining)

6. Isotope Pairs
 Since, we know that when isotopes wish to
become stable the change the particles in
the nucleus through decay.
 The sample before can change into a new
element or isotope
 The parent isotope is the one that decays
and the daughter isotope is on of the
products of the decay.

7. Video
 The Origins Of Spiderman
 Bit by radioactive spider effected by
radioactive decay in a chemistry lab.

8. Quiz
1. What measurement can compare the rate of
radioactive decay?
a) Radiometric dating
b) Radioactive microscope
c) Decay curve
2. How many grams will be left over of a 100 g sample
after 5 half lives?
a) 10.5
b) 3.125
c) 20

9. 7.3 Nuclear Reactions
 A nuclear reaction is when an atom
changes by gaining or releasing particles or
energy. (Can release subatomic particles
and gamma rays)
 This happens because of nucleus wanting
stability by removing particles.
 Bombarding a nucleus with alpha & beta
particles, or gamma rays causes a reaction.
 Scientists can cause a reaction by making
nuclei unstable, causing it make a reaction.

10. Nuclear Fission
 Nuclear fission is the splitting of a heavy
nucleus into two lighter nuclei.
 Heavy nuclei tend to unstable because of
repulsive forces between their many
protons.
 The reactions releases a lot of energy along
with the smaller nuclei and subatomic
particles, from the binding force in the
nucleus.
 Fission is a large source for nuclear power
from it’s energy.

11. Fission Continued
 Some nuclei while undergoing fission
can release subatomic particles, that
can trigger more fission reactions this
is called a chain reaction.
 The number of fissions and the
amount of energy released adds up
quickly that can lead to violent
explosions.
 Fission is used for nuclear
weapons, and nuclear power
generators because of all the energy.
 Since it difficult to control, power
plants monitor and adjust constantly.
 However, it produces radioactive
waste that takes a long time to
decay.

12. Nuclear Fusion
 Nuclear fusion is when a small nucleus combines to
produce a larger nucleus.
 Other subatomic particles and energy is released.
 Fusion occurs in the sun and other stars where
pressure and high temperature causes isotopes of
hydrogen to collide creating enormous amounts of
energy.
 There is no technology capable of using the
energy from fusion reactions. Because it is so strong
from high pressure and temperature, it is impossible
to control.
 It could be used in nuclear weapons as it is seen as
strong.

13. Nuclear Equations
 A nuclear equation is a set of symbols that
indicates changes in the nuclei of atoms
during nuclear reactions.
 The sum of the mass numbers on each side
of the equation stays the same.
 The sum of the charges (atomic numbers)
on each side of the equation stays the
same.

14. Video
• In this episode of spider man; A mad
scientist, Doctor Pretorius, escapes from
prison and plots widespread devastation
with a nuclear weapon he calls "The
Kingdom Come Device."

15. Quiz
1. Where does nuclear fusion occur?
a) In the sun and other stars
b) Under ground
c) Inside a power plant
2. A nuclear reaction can release
a) Gamma Rays
b) Energy
c) Subatomic Particles
d) All of the above
3. A nuclear reaction is induced by
a) alpha & beta particles , and gamma rays
b) energy
c) another atom
4. Nuclear fission releases a very large amount of….
a) energy
b) electrons
c) neutrons