Nuclear ReactionsSection 7.3

The process in which the nucleus changes

gains or releases particles and energy

Nuclear Reactions

The stronger the bond the more energy associated

with itSmall Change = Big

Energy

Chemical reactions involve only the Electrons of atomsNuclear reactions involve the Protons, Neutrons and

Electrons

The Future will Involve Quarks

Energy Output Comparison

Chemical (Burn Coal)Nuclear (Uranium-

235)

2 tonnes (2000Kg) of Coal = 1 g of Uranium Big Energy for such a Small Change

Nuclear energy released is a million times greater than Chemical

Natural or Artificial (man-made)

Nuclear Reactions

Natural: Some isotopes are naturally reactive and

unstable (radioactive decay)

Artificial: scientists can induce (create or speed-up) a nuclear reaction by bombarding a nuclei (making it

unstable) with other nuclei or alpha, beta, and gamma radiation

Types of Nuclear Reactions

Fusion vs. Fission

Fusion• Fusion reaction involves combining particles

• Smashing 2 or more particles together to form a larger one that releases the extra energy

• Two smaller particles have more energy than is needed by one larger particle release the extra

• Think about the energy required(input) and potential(output) from 2 cars (or people) compared to 1 larger car (or person)

• This involves small (light) particles

To Fuse = To Make Whole (One)

Fusion• Fusion is still

experimental (can create but not sustain reactions)

• There are no (independently run) fusion reactors or weapons

• Minimal nuclear waste (formed isotopes are non-radioactive)

• 3 to 4 times more powerful than fission

Naturally occurring (Sun)

Not by man, too costly

Technology is Insufficient (can’t achieve and contain

the high pressures & temperatures)

To Fuse = To Make Whole (One)

Fission• Fission reactions involve breaking apart particles

• Splitting 1 particle into 2 or more, while releasing energy

• Larger particles are more unstable due to the large number of (proton) interactions inside that tear (force) it apart

• Think about being uncomfortable or trapped, a lot of unnecessary energy is wasted and you are glad to release it

• This involves massive (heavy) particles.

To Fizz = To Break-Apart (Pieces)

Fission• Fission is applicable (in

use)• There are nuclear

fission reactors and weapons

• Dangerous radioactive isotope by-products limit fission’s usages

• Disposal of radioactive waste is a problem (dangerous and costly)

Nuclear Power Generation:

Reactors & Weapons

To Fizz = To Break-Apart (Pieces)

Chain Reaction (Explosion)All you need is to start the reaction. After the first, the reaction will continue on its own

Chain reactions are famous for getting out of control

BOOM

The initial particle triggers multiple particles, so the reaction builds (speeds up).

Chain Reaction (Control)To stop the rapid increase that may lead to a violent nuclear reaction

Or use a material to absorb (remove) or moderate (slowdown) the extra bombarding

particles (protons, neutrons, electrons)

Scientists have to either control the fuel in the reaction (the uranium or other fissionable

material)

[A tipping point or a threshold (beginning) of change]

The Importance of IRON in Nuclear Reactions

Fission

As the isotopes become larger the energy released

decreases

Beyond Iron, the isotope requires more energy to

survive (becoming too massive &

unstable)

Fusion

As the split isotopes become

smaller the energy released decreases

Beyond iron, the 2 smaller isotopes

require more energy to survive than the single

larger one

One of the last nuclear reactions that are exothermic

One of the most abundant elements on earth

Neutrons represent a powerful tool for inducing (starting) nuclear reactions

The Importance of Neutrons in Nuclear Reactions

Neutrons are small enough to penetrate matter (fit through holes), but large enough to make a

difference (hit by a car). Neutrons have no overall charge (repulsive forces).

Alpha too big and has protonsBeta smaller and has an electronGamma has (virtually) no mass

Anything else is a combination of no good or we do not have the technology to use it properly

Don’t Forget to Balance!!!!

2 Rules for Writing Nuclear Equations

2. The sum of the atomic charges (in the nucleus) on each side of the equation does not change (stays the

same)

1. The sum of the mass numbers on each side of the equation does not change (stays the same)