The Nucleus of the Atom

Chapter 12

Great Idea:Nuclear energy depends on the conversion

of mass into energy

Chapter Outline

• Empty Space, Explosive Energy• The Organization of the Nucleus• Radioactivity• Energy from the Nucleus

Empty Space, Explosive Energy

Empty Space, Explosive Energy

• Relation of atom to nucleus–What goes on in the nucleus

has almost nothing to do with the atom’s chemistry, and vice versa

–The energies available in the nucleus are much greater than those available among electrons

• Remember E=mc2 ?

iClicker Question

• True or False: Matter cannot be converted into energy.

– A True– B False

iClicker Question

• True or False: What goes on in the nucleus of the atom has almost nothing to do with the atom’s chemistry, and vice versa.

– A True– B False

iClicker Question

• True or False: The energies available among electrons are much greater than those available in the nucleus.

– B True– A False

The Organization of the Nucleus

The Organization of the Nucleus

• Rutherford• Nucleus

–Proton–neutron

• Nucleus gives atom its mass

Atomic Numbers, Isotopes,and the Mass Number

• Atomic number– # of protons in

nucleus• Defines chemical

behavior

• Isotopes– Elements with

different numbers of neutrons

• Mass number– Total protons and

neutrons

The Strong Force

• Strong force–Holds nucleus together–Operates over short distances–Binding energy

Geller’s Subatomic Interlude

Subatomic Interlude II

A Subatomic Interlude III

Subatomic Interlude IIII

A Subatomic Interlude V• Neutrinos are produced

in the “Weak Interaction”, for example– Neutrinos from the earth

• natural radioactivity

– “Man-made” neutrinos• accelerators, nuclear power

plants.

– Astrophysical neutrinos• Solar neutrinos• Atmospheric neutrinos• Relic neutrinos

– left over from the big bang.

Neutrino Detection

Detecting neutrinos requires a differentkind of a detector.

Neutrino Factoids• The earth receives about 40 billion

neutrinos per second per cm2 from the sun.– About 100 times that amount are passing

through us from the big bang.• This works out to about 330 neutrinos in every cm3 of

the universe!• By comparison there are about 0.0000005 protons per

cm3 in the universe.

• Our body emits about 340 million neutrinos per day from 40K.

• Neutrinos don’t do much when passing through matter.

• Remember, it is very difficult to observe neutrinos.

Neutrino Detection II

• The neutrino is observed by detecting the product of its interaction with matter.

νe Electron

νμ Muon

Neutrinos reveal information about the Sun’score—and have surprises of their own

• Neutrinos emitted in thermonuclear reactions in the Sun’s core have been detected, but in smaller numbers than expected

• Recent neutrino experiments explain why this is so

iClicker Question

• A subatomic particle with a charge of +1 is called a:

– A proton– B neutron– C electron

iClicker Question

• A subatomic particle with a charge of zero is called a:

– A proton– B neutron– C electron

iClicker Question

• Two atoms with the same number of protons, but different numbers of neutrons are called:

– A isomers– B isotopes– C ions

iClicker Question

• The attractive force holding particles together in the nucleus is called the:

– A weak force– B medium force– C electromagnetic force– D strong force

iClicker Question

• Which subatomic particles are located in an atom’s nucleus?

– A protons and electrons– B electrons and neutrons– C neutrons and protons– D neutrons only

Radioactivity

What’s Radioactive?

• Radioactivity or radioactive decay• Radiation

The Kinds of Radioactive Decay

• Alpha Decay– Release of particle

• Composed of 2 protons and 2 neutrons

• Beta Decay– Emission of electron– Neutrino– Effect– Weak Force

• Gamma Radiation– Electromagnetic

radiation

Moving Down the Chartof the Isotopes

Radiation and Health• Ionization

–Stripping electron(s)

• Long-term effects–Cancer–Birth defects

Half-Life

• Half-life–Average time for decay of ½ batch of

radioactive isotopes

• Wide range of half-lives• Cannot predict half-life

Radiometric Dating

• Radiometric dating–Measurement of half-

life

• Carbon-14–Half-life = 5700

years

• Geology–Need longer half-

lives

Decay Chains• Decay chains

–Series of decays–Continues until stable isotope appears

Indoor Radon

• Decay of Uranium-238• Radon-222

–Can build up– Increase ventilation

iClicker Question

• The spontaneous release of energetic particles is called:

– A electron diffusion– B magnetic repulsiveness– C fusion– D radioactivity

iClicker Question

• Alpha decay involves emission of which particle?

– A electron– B helium-4 nucleus– C gamma ray

iClicker Question

• Beta decay involves emission of which particle?

– A electron– B helium-4 nucleus– C gamma ray

iClicker Question

• Which statement about radiation and health is most correct?

– A Radiation is extremely hazardous in small amounts and kills many people shortly after exposure.

– B Only in unusual circumstances, such as the aftermath of nuclear weapons used on Hiroshima and Nagasaki, or the nuclear reactor accident at Chernobyl do people die shortly after exposure.

– C There are no recorded examples of human deaths occurring shortly after exposure to radioactivity.

iClicker Question

• Consider a 10.0 gram sample of an isotope which has a half-life of 15 minutes. What amount of the sample is left after 1 hour?

– A none– B 2.5 grams– C 0.625 grams– D 15.0 grams

Energy from the Nucleus

Nuclear Fission

• Fission–Splitting of nuleus

• Nuclear Reactor–Extracts energy

• Meltdown

Fusion

• Fusion–2 atoms of H combine

to form He–Some mass

converted to energy

• Sunlight

iClicker Question

• The only significant difference between a nuclear reactor and a coal-fired generating plant is:

– A the turbine must spin at a much higher rate

– B the way the generator turns is in a clockwise direction

– C the way in which the steam is generated

iClicker Question

• Would you ever consider living close (within 20 miles) to a nuclear power plant?

– A yes– B no

iClicker Question

• Do you believe the government should spend more money to develop nuclear fusion reactors to produce energy?

– A yes– B no