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Chemistry 105 > Chap. 5: The Atomic Nucleus > Flashcards

Chap. 5: The Atomic Nucleus Flashcards

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1
Q

Is nuclear energy clean?

A

No, there is radioactive waste.

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2
Q

Where is nuclear waste stored?

A

Yucca Mountain

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3
Q

Yucca Mountain

A
  • Located 80 miles NW of Las Vegas.
  • Waste is stored deep underground.
  • It is designed to be a long term storage facility.
  • Approved in 2002 by Congress.
  • Funding was terminated in 2011 (thanks to Harry Reid).
  • High probability that Yucca Mountain will continue.
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4
Q

Nevada Test Site

A
  • Located 65 miles NW of Las Vegas.
  • Above-ground and underground testing.
  • Testing from 1951 to 1992.
  • 1,021 nuclear detonations; 921 underground detonations.
  • Long-term health and environmental impacts.
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5
Q

Environmental Impacts of Testing Sites

A
  • Above-ground detonations blast radioactive materials into the air, which gets carried away by the wind and deposited, causing a nuclear fallout.
  • Underground detonations contaminate soil and water and blast giant caverns underground.
  • These areas remain contiminated to this day.
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6
Q

How bad are these testing sites?

A
  • Radiation levels are on the order of 100,000 times that of accepted levels.
  • The longer the isotopes survive, the greater the risks (isotopes can live up to 10,000 years!).
  • There is no “immediate” health threat.
  • Nevada is ranked as Low Priority for clean up.
  • Only 48 water wells are currently monitored.
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7
Q

Two types of isotopes:

A
  1. Stable Isotopes – Optimum ratio of neutrons and protons.
  2. **Unstable Isotopes **– Ratio of neutrons and protons is either too high or too low. The unstable isotope will change in a way to RESTORE the balance between neutrons and protons.

— RADIOACTIVE

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8
Q

Radiation Types

A

**Alpha Particle (α) **

Beta Particle (ß)

Gamma Rays ( ɣ )

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9
Q

Alpha Particle

α

A

– Heavy (large, massive)

– Positive ( + ) electric charge

– Helium w/o electrons

– Alpha particles are emitted when the nucleus wants to get into a more STABLE environment (Alpha Decay)

– Alpha particles are TWO protons and TWO neutrons (which is helium, He, on the periodic table)

2He

<span><span>2</span></span>

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10
Q

Beta Particle

ß

A

– Light

– Negative ( – ) electric charge

– Just an emitted electron

– Moves really fast

– Beta particles (electrons) are emitted from a neutron, and that neutron turns into a proton in order to stabilize the nucleus (Beta Decay)

0 e

–1

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11
Q

Gamma Rays

ɣ

A

– No mass

– Pure energy

– Can travel far distances

– EXTREMELY DAMAGING

0ɣ

0

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12
Q

How much damage can alpha particles do to the human body?

A

They can only cause surface (external) damage. Alpha particles lack the energy to penetrate the skin.

If, however, the alpha particles are inhaled or swallowed, the internal tissues will be affected and the risk of cancer increases (specifically lung cancer).

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13
Q

How much damage can beta particles do to the human body?

A

Both acute and chronic health effects. Acute exposures are uncommon. Contact with a strong beta source from an abandoned industrial instrument is the type of circumstance in which acute exposure could occur. Chronic effects are much more common.

Chronic effects result from fairly low-level exposures over a long period of time. They develop relatively slowly (5 to 30 years for example). The main chronic health effect from radiation is cancer. When taken internally beta emitters can cause tissue damage and increase the risk of cancer.

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14
Q

How much damage can gamma rays do to the human body?

A

Because of the gamma ray’s penetrating power and ability to travel great distances, it is considered the primary hazard to the general population during most radiological emergencies.

In fact, when the term “radiation sickness” is used to describe the effects of large exposures in short time periods, the most severe damage almost certainly results from gamma radiation.

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15
Q

How can we make alpha particles less dangerous?

A

Add 2 electrons to them so that they can become helium.

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16
Q

How can we make beta particles less dangerous?

A

We must slow the particles down and incorporate them into whatever atom we have.

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17
Q

How do we protect ourselves from alpha particles?

A

We must wear really thick clothing.

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18
Q

How do we protect ourselves from beta particles?

A

We must use a material that is sturdier than thick clothing, like a thin metal sheet.

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19
Q

How do we protect ourselves from gamma rays?

A

Wearing a thick, lead apron, like the ones the x-ray technicians put on you before taking your x-ray.

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20
Q

What makes a nucleus unstable?

A

The balance of protons and neutrons in a nucleus determines whether a nucleus will be stable or unstable. Too many neutrons or protons upset this balance, disrupting the binding energy from the strong nuclear forces making the nucleus unstable.

  • **Electrostatic forces (ESF) **

– Positive ( + ) repels positive ( + )

  • **Strong Nuclear Force (SNF) **

– Attractive force between nucleons (protons and neutrons)

– Felt over short distances, between 1 and 3 femto (f or 10-15).

– SNF > ESF

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21
Q

Short Distance

A
  • ​SNF > ESF (Strong Nuclear Force > Electrostatic Force).
  • 1 – 3 fm.
  • A strong nuclear force in which the proton and electron ATTRACT each other because of their short distance from each other.

​(Refer to the nuclei on the RIGHT in the attached image)

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22
Q

Farther Distance

A
  • ESF > SNF (Electrostatic Force > Strong Nuclear Force)
  • > 3 fm

​(Refer to the nuclei on the LEFT in the attached image)

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23
Q

Anything that is (less than / greater than) lead is too (big / small) to sustain itself.

A

Anything that is GREATER THAN lead is too BIG to sustain itself.

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24
Q

Is helium (He) stable or unstable?

A

STABLE

SNF > ESF

25
Q

Is uranium (U) stable or unstable?

A

UNSTABLE

ESF > SNF

26
Q

Types of Radioactive Decay

A
  1. **Alpha (α) Decay **– Produces an alpha particle when the nucleus emits TWO protons and TWO neutrons (which makes helium).
  2. Beta (ß) Decay – Produces a beta particle when a neutron emits an electron in order to turn into a proton.
27
Q

All elements with an atomic number of 82 and larger will undergo

_________ because they are too large.

A

Radioactive decay

28
Q

(Light / Heavy) elements are the most stable with the same number of protons and the same number of neutrons.

A

Light elements are the most stable with the same number of protons and the same number of neutrons.

29
Q

As elements get bigger, we need more _______ to stabilize the nucleus.

A

Neutrons

30
Q

Half-Life Decay

A

Radioactive isotopes decay at different rates. The radioactive decay rate is measured in terms of a characteristic time, the half-life. They are constant and are NOT affected by external conditions.

The half-life of a radioactive material is the time required for half of the radioactive atoms to decay.

Example:

Radium-226 has a half-life of 1620 years. This means that half of any given specimen Ra-226 decays by the end of 1620.

31
Q

If a sample of radioactive isotopes has a half-life of 1 day, how much of the original sample will remain at the end of the second day? The third day?

A

At the end of the second day: 1/4 of the original sample will be left. The 3/4 that underwent decay becomes a different element altogether.

At the end of the third day: 1/8 of the original sample will remain.

32
Q

Which will give a higher counting rate on a radiation detector — radioactive material that has a short half-life or a long half-life?

A

The material with the short half-life is more active and will show a higher counting rate on a radiation detector.

33
Q

Radiation Detector

A

A device that accurately estimates the half-life of an element.

The SHORTER the half-life of a substance, the faster it disintegrates and the more radioactive per minute is detected.

34
Q

How does radioactivity allow archeologists to measure the ages of ancient artifacts?

A

Carbon-14 Dating.

The artifact’s current radioactivity level is being measured.

ALL animals eat either plants or plant-eating animals; therefore, all animals, including humans, have a little carbon-14 in them. That is why all living things on earth have carbon-14 in them.

The half-life of carbon-14 is 5730 years, meaning that half of the carbon-14 atoms now present in a plant or animal that dies today will decay in the the next 5730 years. Half of the remaining carbon-14 atoms will decay in the next 5730 years and so on. With this knowledge, scientists are able to calculate the age of carbon-containing artifacts, such as wooden tools or skeletons.

35
Q

Nuclear Fission

A

The splitting of an atom’s nucleus into two smaller halves.

Nuclear fission powers bombs and power plants.

Nuclear fission involves the delicate balance between two forces within the nucleus.

— One force is the strong nuclear force, which is a force that holds all the nucleons together.

— The second force is the repulsive electric force occurring among all the like-sign protons.

— SNF < Repulsive Forces

In most nuclei strong force dominates. In uranium, however, this domination is weak.

36
Q

Explain how the explosions from atomic bombs are produced.

A

Nuclear fission is taking place, in which the nucleus of an atom is split, releasing energy and radioactivity.

Fission occurs when an atom of a heavy element (i.e. one that has a large atomic mass) splits into atoms of lighter elements.

The products of the reaction have less mass than the starting atom. This difference in mass is from the energy and the radioactivity that has been released.

Example:

Uranium-235 is a naturally occurring radioactive element. In a fission reaction, uranium-235’s nucleus absorbs a neutron moving at a slow speed. This neutron causes uranium-235’s nucleus to become reactive, or “destabilize.”

The destabilized nucleus splits, transforming uranium-235 into lighter elements like krypton and barium. Also released are energy, radioactivity and multiple fast-moving neutrons.

These neutrons will then go on to start another reaction with more uranium atoms; this is called a chain reaction. An uncontrolled chain reaction releases huge amounts of energy. These huge amounts of energy is what powers atomic bombs.

37
Q

What are some other uses for the energy produced by nuclear fission?

A

In nuclear power plants, the heat energy released from a uranium fission reaction is used to turn water into steam. This steam is used to turn turbines, which, in turn, generate electricity.

Engineers control the rate of fission by using graphite rods to absorb the extra neutrons that are produced.

38
Q

The equation for a typical uranium fission reaction:

A

Note that in this reaction, 1 neutron starts the fission of a single uranium nucleus, which produces nuclear fragments and 3 neutrons. These 3 neutrons can cause the fissioning of 3 more uranium atoms, releasing 9 more neutrons. If each of these 9 neutrons succeeds in splitting a uranium atom, the next step in the reaction produces 27 neutrons, and so on.

This is called a chain reaction.

(Page 146-147, Conceptual Chemisty textbook by John Suchocki)

39
Q

Chain Reaction

A

A self-sustaining reaction in which the products of one reaction event initiate further reaction events.

Chain reactions are more effective in large chunks of uranium than in smaller chunks.

40
Q

Why are chain reactions more effective in large chunks of uranium rather than in small chunks of uranium?

A

In smaller chunks, neutrons easily find the surface and escape. As the neutrons escape, the chain reaction no longer builds up.

Basically, in a small piece of pure uranium, a chain reaction runs its course before it can cause a large explosion, because the neutrons leak from the surface too soon.

41
Q

What happens when you suddenly push two small chunks of uranium together?

A

They make a larger chunk, where neutrons are no longer able to escape as easily. Instead, they continue the chain reaction, which becomes sustainable.

42
Q

Critical Mass

A

The minimum size of a chunk of uranium needed for a sustainable chain reaction.

Any chunk at or above the critical mass produces a steady release of energy.

43
Q

Why is it difficult to construct a fission bomb?

A

The difficulty is in seperating enough uranium-235 from the more abundant uranium-238. Besides the slightly different masses, the two isotopes have the same physical and chemical properties.

It took scientists more than 2 years to extract enough of the 235 isotope from uranium ore to make the bomb that was detonated at Hiroshima in 1945.

44
Q

What is a disadvantage of fission power?

A

The radioactive waste products.

45
Q

What are some advantages of fission power?

A
  • Plentiful electricity
  • Conservations of the many billions of tons of fossil fuels that every year are literally turned to heat and smoke
  • The elimination of the megatons of sulfur oxides and other poisons that are put into the air each year by the burning fossil fuels.
46
Q

Nuclear Fusion

A

The combining of two light nuclei to make one heavy nucleus.

Energy is GAINED.

When two small nuclei fuse—for example, a pair of hydrogen isotopes—the mass of the resulting helium nucleus is less than the mass of the two small nuclei before fusion.

The mass difference is released in the form of energy.

Example:

Hydrogen-2 + Hydrogen-3 = Helium-4 and a neutron

47
Q

How do fusion reactions occur?

A

The nuclei must collide with one another at a very high speed in order to overcome their mutual electric repulsion.

The speed corresponds to temperatures—the higher the temperature, the more successful the fusion reaction.

Fusion brought by high temperatures is called thermonuclear fusion.

48
Q

Thermonuclear Fusion

A

Fusion brought about by high temperatures. Nuclear burning.

Thermonuclear fusion is the energy source of our sun, which is, in turn, the ultimate energy source of life on earth.

In the sun, ~657 million tons of hydrogen is converted into 653 million tons of helium a second. The missing 4 million tons of mass is converted into energy—a tiny bit of which reaches our planet as sunshine.

49
Q

What is the first thermonuclear bomb?

A

The Hydrogen Bomb.

Detonated in 1952.

Whereas the critical mass of fissionable materials limits the size of an atomic bomb, no such limit is needed for a hydrogen bomb.

Just as there is no limit to the size of an oil-storage depot, there is no theoretical limit to the size of a hydrogen bomb. Just like the oil in the storage depot, any amount of fusion fuel can be stored with safety until ignited.

50
Q

To get a release of nuclear energy from iron, should iron undergo nuclear fission or fusion?

A

Neither.

Iron is at the very bottom of the “energy valley.” No energy is released.

51
Q

Review:

What is an isotope?

A

When an atom has an unequal number of neutrons from the protons.

Example:

An atom that has more protons than neutrons, or more neutrons than protons.

52
Q

Does nuclear fusion break the law of Conservation of Energy?

The law states that energy cannot be created or destroyed, but aren’t you creating energy if you get back more energy than you put into it?

A

If you consider mass as a form of energy, which you should according to Einstein’s E=mc2 equation, then the law IS NOT broken.

With a nucleus, some of the mass of the proton/neutrons is converted into energy. This energy is required to hold the protons and neutrons together. For example, the mass of 2 individual protons and 2 individual neutrons is greater than the mass of a helium nucleus (2 protons and 2 neutrons).

When you fuse two light elements, some of this energy is given off.

53
Q

Carbon Dating

A
  • Carbon dating is used to determine the age of organic materials.
  • Carbon-14 (14C) is being measured from the sample.
  • Carbon dating can date back to 60,000 years!
  • The half-life of Carbon-14 is 5730 years.
54
Q

What are some natural sources of radiation?

A
  • Sun
  • Earth
  • Air
55
Q

What are some man-made sources of radiation?

A
  • Medical instruments (x-rays, etc.)
  • Weapons (bombs, etc.)
56
Q

What are the advantages of nuclear fission?

A
  • Tons of energy is produced.
  • Has been in practice for a while.
57
Q

What are the disadavantages of nuclear fission?

A
  • Tough to control.
  • Waste and storage can be a problem.
  • Uranium will eventually run out.
58
Q

What are the advantages of nuclear fusion?

A
  • Tons and tons of energy is produced.
  • Zero waste.
  • Materials will NEVER run out.
59
Q

What are the disadvantages of nuclear fusion?

A
  • Dangerously high temperatures.
  • Difficulty to control.

Chemistry 105 (10 decks)

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