Nuclear Reactions

Chapter 10

Standards

• SPS3. Students will distinguish the characteristics and components of radioactivity

• SPS3a. Differentiate among alpha and beta particles and gamma radiation.

• SPS3b. Differentiate between fission and fusion.• SPS3c. Explain the process half-life as related to

radioactive decay.• SPS3d. Describe nuclear energy, its practical

application as an alternative energy source, and its potential problems.

Nuclear Radiation

Radioactive Decay: unstable isotopes emitparticles and release energy to become stableisotopes.• after radioactive decay, the element changes

into a different isotope of the same element or into an entirely different element.

Radiation

Nuclear Radiation: particles and energyreleased from the nucleus during radioactivedecay.

He42

Types of Radiation

• Alpha () -protons and neutrons paper2+

• Beta-minus (-) -electrons and positrons e0-1 1- lead

• Gamma () -high-energy photons 0 concrete

Types of Nuclear Radiation (pg 238)Radiation

Type Symbol What is it? Mass (kg) ChargeTravel depth

through materials

Alpha particle

2 protons and 2

neutrons

6.646x10-27 +2

Least far due to

massive size

Beta particle

Fast-moving

electrons or positrons

9.109x10-31 -1, (+1)

Farther than alpha, but still not

far

Gamma ray Form of

electromagnetic energy

None 0

Through clothes;

Can cause harm

NeutronA neutron

leaving the nucleus

1.675x10-27 0

Penetrate the

farthest

Nuclear Decay

• Anytime an unstable nucleus emits alpha or beta particles, the number of protons and neutrons changes.

• Alpha decay: atomic mass and number change

• Beta decay: atomic number changes• Gamma decay: energy of the nucleus is lower,

but no change in atomic number or mass

Nuclear Decay

• Why nuclide (nucleus of an isotope) decay… to obtain a stable ratio of neutrons to protons

K

K4019

3919

Stable

Unstable(radioactive)

Alpha Decay

22688 +Ra 4 He2

22286 Rn

226 = 222 + 488 = 86 + 2

(atomic mass & atomic number change)

Beta Decay Equations

146 +C 0 e-1

14 7 C

14 = 14 + 06 = 7 + (-1)

(atomic mass stays the same; atomic number changes by 1)

Actinium-217 decays by releasing an alpha particle. Write the equation for this decay process and determine which element is formed.

227

89+Ac 4 He2

A

Z X

Complete the following radioactive-decay equation. Identify the isotope X. Indicate whether alpha or beta decay takes place.

63

28+ Ni 0 e-1

AZ X

Radioactive Decay Rates

• Half-life: time in which half of a radioactive substance decays; measure of how quickly a substance decays.

-Iodine-131: used by doctors to diagnose medical problems

-Potassium-40: used by geologists to predict the age of rocks

Calculating Half-Life

• Radium-226 has a half-life of 1599 years. How long will 7/8 of a sample take to decay?1. Find out how much will be left. 8/8 - 7/8 = 1/8 left over2. Calculate how many half-lives until only 1/8 is left.

1 1/2 1/4 1/8

One half life Two half lives Three half lives

3. Calculate how many years it will take for 3 half lives to occur.

1599 x 3 = 4797 years

Nuclear Fission• Nuclear fission: the process by which a

nucleus splits and neutrons and energy are released.

• Nuclear chain reaction: a continuous series of fission reactions (pg 340)

Nuclear Fusion• Nuclear fusion: when 2 light nuclei combine

to form a heavier nuclei -Hydrogen is turned into Helium on the sun. (pg 342)

Radiation on Earth

• All around you.• Background radiation: arises naturally from

the sun, soil, rocks, and plants• You are exposed to more radiation in the

mountains than at sea level

Beneficial Uses of Radiation• Smoke detectors release alpha particles• Radiation is used in x rays, MRIs, CT scans, PET

scans, and ultrasounds• Radiation therapy is used to treat cancer• Used in agriculture to track the flow of water

Nuclear Radiation Risks

• High levels of radiation exposure can cause radiation sickness

• High concentrations of radon gas can cause cancer

Nuclear Power

Advantages Disadvantages

Does not produce greenhouse gases

Radioactive products must be handled and stored carefully so

they do not escape.

Much more energy available in uranium reserves than gas and

coal.Expensive to build due to many

safety regulations.

Waste must be stored in areas away from people, homes,

water, earthquakes.