Modern Physics

Radioactive Decay

Radioactive Decay

Look at the periodic table given to you. Find element with the atomic number 6What is it?

Radioactive Decay

The element with the atomic number 6 is CarbonLook at the atomic mass below the word CarbonWhat is it?

Radioactive Decay

The mass is 12.011 amu. Remember that protons and neutrons are about 1 amu eachTherefore you canassume that thereare 12 particles inthe nucleus,6 protons6 neutrons

Radioactive Decay

You would then write the nuclear symbol for Carbon – 12 as 12

6C (with the 6 over the 6)

Radioactive Decay

Find Oxygen on the chart.

Radioactive Decay

Find Oxygen on the chart.Atomic number 8. How many protons does oxygen have?

Radioactive Decay

Find Oxygen on the chart.Atomic number 8. How many protons does oxygen have?Yes – 8 protonsHow many neutronsdoes the most common Isotope ofOxygen have?

Radioactive Decay

Find Oxygen on the chart.Atomic number 8. How many protons does oxygen have?Yes – 8 protonsHow many neutronsdoes the most common Isotope ofOxygen have? 8

Radioactive Decay

Find Argon on the chart. Number 18

Radioactive Decay

Find Argon on the chart. Number 18How many protons does it have?

Radioactive Decay

Find Argon on the chart. Number 18…How many protons does it have? 18I think youare getting it. How many totalProtons andNeutrons?

Radioactive Decay

Find Argon on the chart. Number 18…How many protons does it have? 18I think youare getting it. How many totalProtons andNeutrons? 40

Radioactive Decay

• Write the symbols for the following atoms most common isotope.

• Fluorine(9)

• Neon(10)

• Sodium(11)

• Radon(86)

• Uranium(92)

Radioactive Decay

• Review from yesterday• An atom is stable (not radioactive) if it is in the

belt of stability• An atom is unstable (radioactive) if it is

outside the belt of stability• All elements beyond number 83, Bismuth are

unstable - WHY?

Radioactive Decay

• Above element 83, the protons are farther and farther away from each other in the nucleus, therefore requiring a greater nuclear force to overcome the electrostatic repulsive forces. The nuclear force is not strong enough to hold together the protons when more than 83 of them are packed into a nucleus.

Radioactive Decay

• Three types of radioactive decay

• 24α alpha particle decay also shown as 2

4He

•-1

0ß Beta particle decay (An electron from a neutron)

•+1

0ß Positron emission (a positively charged electron)

• ϒ gamma ray High energy electromagnetic waves

Radioactive Decay

• 24α alpha particle decay also shown as 2

4He

An alpha particle is two protons and two neutrons bound together and emitted from the nucleus. Alpha particle are identical to a helium nuclei and have a charge of 2+

Radioactive Decay

•1

0ß Beta particle decay

• A beta particle is actually an electron emitted from the nucleus. To create a beta particle, a neutron converts itself into a proton and ejects the right combination of quarks to make an electron

Radioactive Decay

•+1

0ß Positron emission

• Elements below the belt of stability have too many protons. To decrease the number of protons, a proton emits a positron, or positively charged electron

Radioactive Decay

• Not a decay per say, but another way to get rid of too many protons, is Electron Capture

• In electron capture, an inner orbital electron is captured by the nucleus of its own atom. This electron combines with a proton and forms a neutron.

Radioactive Decay

Radioactive Decay