Chapter 31

Nuclear Physics and Radioactivity

31.1 Nuclear Structure

The atomic nucleus consistsof positively charged protonsand neutral neutrons.

31.1 Nuclear Structure

neutrons

ofNumber protons

ofNumber neutrons and

protons ofNumber

NZA

atomicnumber

atomic massnumber

31.1 Nuclear Structure

Nuclei that contain the same number of protons but a differentnumber of neutrons are known as isotopes.

31.1 Nuclear Structure

3115 m102.1 Ar

31.2 The Strong Nuclear Force and the Stability of the Nucleus

The mutual repulsion of the protonstends to push the nucleus apart. Whatthen, holds the nucleus together?

The strong nuclear force.

31.2 The Strong Nuclear Force and the Stability of the Nucleus

As nuclei get larger, more neutrons are required for stability.

The neutrons act like gluewithout adding more repulsiveforce.

31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy

22deficit Massenergy Binding cmc

31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy

Example 3 The Binding Energy of the Helium Nucleus Revisited

The atomic mass of helium is 4.0026u and the atomic mass of hydrogenis 1.0078u. Using atomic mass units, instead of kilograms, obtain thebinding energy of the helium nucleus.

31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy

u 0304.0u 0026.4u 0330.4 m

MeV 5.931u 1

MeV 3.28energy Binding

31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy

31.4 Radioactivity

A magnetic field separates three types of particles emitted byradioactive nuclei.

31.4 Radioactivity

α DECAY

He D P 22

42

AZ

AZ

31.4 Radioactivity

A smokedetector

31.4 Radioactivity

β DECAY

e D P 011 A

ZAZ

31.4 Radioactivity

γ DECAY

P P AZ

AZ

excited energystate

lower energystate