NUCLEAR DECAY NOTESALPHA, BETA, GAMMA

How do you pronounce N-U-C-L-E-A-R?

What we already know

⦿ What are atoms?

⦿ What does the atomic structure look like?

⦿ What are ions?

⦿ What are isotopes?

Radioactivity

⦿ What is radioactivity?○ refers to the particles which are emitted from

nuclei as a result of nuclear instability

⦿ What makes something radioactive?○ Unstable isotopes

⦿ Where do we see radioactivity around us?

⦿ Is radioactivity dangerous to us?

Nuclear Decay (Radiation)

⦿ There are 3 types of radiation that can

occur

● 1. Alpha decay – helium nuclei emitted from

a radioactive atom

● 2. Beta decay – fast moving electron

formed by decomposition of a neutron on an

atom

● 3. Gamma decay – high energy

electromagnetic radiation

Characteristics of Radiation

Property Alpha Decay Beta Decay Gamma

Radiation

Composition Alpha Particle

(Helium Nucleus)

Beta Particle

(Electron)

High Energy

Electromagnetic

Radiation

Symbol γ

Charge +2 -1 0

Mass 4 amu 1/2000 amu 0

Penetrating Distance of Radiation

What makes something radioactive?

⦿ Unstable nuclei

⦿ Comes from the proton to neutron ratio○ (commonly referred to as magic numbers)

⦿ For elements with atomic number <20 the ratio is 1:1

⦿ For elements with atomic number >20 the ration is ~ 1:1.5

⦿ Any higher than ~ 1:1.5 typically is radioactive

Alpha and Beta Decay

⦿ We will mostly focus on alpha and beta

decay in this class

⦿ Characteristics:

● Alpha decay decreases protons and

neutrons by 2

● Beta increase in protons and decrease in

neutrons

⦿ Let’s look at examples!!!!!

Alpha Decay

Protons/

Atomic #Protons/

Atomic #

Protons/

Atomic #

Neutrons/

Atomic Mass

Neutrons/

Atomic MassNeutrons/

Atomic Mass

Beta Decay

Protons Protons

Atomic Mass Atomic Mass

Half-Life

⦿ Half-Life

● The time required

for half of the atoms

of a radioisotope to

emit radiation and

decay to products

● In other words, how

long until half of the

material no longer

exists

Half-Life Problem

⦿ Nitrogen-13 has a half-life of 10 minutes.

N-13 undergoes beta decay to become

C-13. Assume you start with 2.00 grams

of N-13.

● How long is four half-lives?

● How many grams of N-13 would remain

afterN-13 has undergone 3 half-lives?

Half Life Problem

⦿ 1 half-life is 10 minutes. So 4 half-lives

should be

● 4 X 10 minutes = 40 minutes

⦿ You should map out half life problems

like this:

2.00 grams

N-130.25 grams

N-13

0.50 grams

N-13

1.00 grams

N-131st half-life 2nd half-life 3rd half-life

Try it on your own

⦿ How much of a 100.0 g sample of Au-

198 is left after 8 days if gold’s half-life is

2 days?

Fission vs. Fusion

⦿ Fusion

● Fusing nuclei

● Makes heavier

elements

● Requires high

temperature

● Releases more

energy than fission

● Used in H-bomb

⦿ Fission

● Splitting nuclei

● Makes lighter

elements

● Occurs at room

temperature

● Releases energy

● Used in nuclear

weapons

Fusion

⦿ Fusion● Combining 2

elements together

● Occurs naturally in the sun

● Ideal energy source

● Abundant supply of hydrogen

● Nonpolluting waste product