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CHEMISTRY 1 Nuclear Chemistry Chapter 28
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CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Jan 12, 2016

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Page 1: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

CHEMISTRY 1Nuclear Chemistry

Chapter 28

Page 2: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

NUCLEAR CHEMISTRY

1896- Antoine Becquerel discovered ___________________

He accidently left uranium ore on top of photographic plates. They became fogged from the exposure. Becquerel had 2 graduate students: _______________ _______________

radioactivity

Marie &Pierre Curie

Page 3: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

_______________________- the property by which uranium gives off rays

______________________-penetrating rays emitted by a radioactive source.

In 1903, the Curies and Becquerel won Nobel prizes for this discovery.

Radioactivity

Radiation

Page 4: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Types of Radiation 1. Alpha emission -helium nuclei emitted from a

radioactive source 2 protons & 2 neutrons 2+ charge Symbol is Don’t travel far and are not very penetrating Stopped by a sheet of paper Can’t penetrate skin, but dangerous if ingested Very common with heavy nuclides

2

4He

Write this

Page 5: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Alpha Decay (α)

Lose 2 protons (+2 charge) & 2 neutrons

He42

Page 6: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Examples:

U ___ + He234

904

2

Ra Rn + He 2

4

88

226 222

86

23892 Th

Law of conservation of mass

Atomic #

Mass # = # protons + # neutrons

Page 7: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

226 88

42

222 86

Ra Rn + He

Atomic # 88 86 + 2

Mass # 226 222 + 4

Page 8: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

2. Beta emission - fast moving ___________ formed by the decomposition of a neutron of an atom. The neutron breaks into a proton and an electron. The proton stays in the nucleus and the electron is ejected. (net effect: neutron changes into proton) Write this:

n H + e0

1 1

1 1

0

electrons

Page 9: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Much smaller than alpha particles Symbol is Charge is -1 Much more penetrating than alpha particles Stopped by aluminum foil or thin pieces of

wood

1

0

C N + e 6

14

7

14

1

0

e

Write this

Page 10: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Beta Decay (β)

Lose electron (-1 charge, no mass)

β 0-1

C N + β14 6

14 7

0-1

Page 11: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.
Page 12: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

3. Gamma emission - _________________ _____________ (high energy) emitted from a nucleus as it changes from an excited state to a ground energy state. Often emitted along with or radiation Symbol is Has no mass & no charge High energy photon

U He + Th + 2 92

238 4

2

234

90

electromagneticradiation

Page 13: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

the emission of gamma rays is one way that a nucleus with excess energy (in an excited nuclear state) can relax to its ground state

Extremely penetrating, very dangerous Stopped somewhat by several feet of concrete or

several inches of lead

Page 14: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Gamma Emission (γ)

γ00

No mass, no charge, loses just energy

Page 15: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

4. Positron emission- ___________________________________ e Antimatter Net effect: changes proton to a neutron Occurs when neutron/proton ratio is too small

10

22

0

1

0

1 Na e + Ne 11

22

Particle with the mass of an electron but a positive charge

Write this (the 0 and the +1)

Page 16: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Alpha radiation cannot penetrate the skin and can be blocked out by a sheet of paper, but is dangerous in the lung.

Beta radiation can penetrate into the body but can be blocked out by a sheet of aluminum foil.

Gamma radiation can go right through the body and requires several centimeters of lead or concrete, or a meter or so of water, to block it.

Page 17: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.
Page 18: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Make sure you have both of these things: Calculator Periodic Table

Page 19: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Nuclear Transformation (Transmutation)- ____________________________________ bombarding with alpha particles

Bombarding with neutrons

N + He O + H 14

7

4

2

17

8

1

1

U + n U 238

92

1

0

239

92

Changing one element into another

Write these

Page 20: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Fill in the blanks (not in your notes):

1. Co Ni + ____

2. Am Np + ____

3. Th He + ____

4. N + ____ C + H

6027

6026

0 1

241 95

237 93

42

11

14 6

14 7

230 90

42

226 88 Ra

10 n

He

e

Page 21: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.
Page 22: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Half-life (t1/2)

the time required for ½ of the atoms of a radioisotope to emit radiation and decay to products

the longer the half-life, the more _____________ the isotope

varies from fractions of a second to millions of years

stable

Page 23: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Examples Nitrogen-13 decays to carbon-13 with a half-

life of 10 minutes. How long is 4 half lives?

4 half lives X 10 min/half life =

40 min.

Page 24: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

If you start with 2.00 g of nitrogen-13 how many grams will remain after 4 half lives?

2.00 g 1.00 g 0.500 g 0.250 g

0.125 g

4

321

Page 25: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Phosphorous-32 has a half-life of 14.3 yr. How many grams remain after 57.2 yr from a 4.0 g sample?

57.2 yr

14.3yr / half-life= 4 half-lives

4.0 g 2.0 g 1.0 g 0.50 g321

0.25 g4

Page 26: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Carbon-14 dating

Carbon-14 is continuously produced in the ____________ when high energy neutrons from outer space collide with nitrogen-14 in the air.

N + n C + H 14

7

1

0

14

6

1

1

atmosphere

Page 27: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Carbon-14 combines with oxygen to form CO2 which is incorporated into plant materials. As long as the plant or animal is alive, decaying carbon-14 is continuously replaced. After death, the carbon-14 decays at a steady rate. Carbon-14 decays to Nitrogen-14

C e + N 14

6

0

114

7

Page 28: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

The proportion of carbon-14 in the atmosphere is relatively constant. The carbon-14/carbon-12 ratio is used to identify the age of wood, cloth and other ______________ artifacts. The half-life of carbon-14 is _______________ years.

Only works for organic materials Adjusted for change in % C-14 over the years

organic5730

Page 29: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Example

If the C-14 in a fossil sample is only 1/4 what it is in living organisms, how old is the object?

To have ¼ remaining, 2 half lives have passed.

2 X 5730 yr =

11,460 yr.

Page 30: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Fission - splitting a heavy nucleus into two nuclei with smaller mass numbers.

used for _____________________

production of ______________causes a chain reaction (which must be controlled)

1 kg of uranium-235 is equivalent to 20,000 tons of dynamite

nuclear energy

n + U Ba + Kr + 3 n 1

0

235

92

142

56

91

361

0

neutrons

Page 31: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Fission – splitting of atoms.FISSION: splitting of atoms

Page 32: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Fission in a nuclear reactor is carefully controlled. Much of the energy is _______. This energy is used to produce _________ and subsequently, __________________.

A _________________(usually water) is needed. The water (or carbon) also acts as a moderator. It

_____________the neutrons down so that they can be captured by the U-235 fuel.

Control rods made of _______________ are present to absorb excess neutrons to slow down the reaction. They can be raised or lowered into the reactor core.

heatsteam

electricitycoolant

slows

cadmium

Page 33: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Fusion- combining two light nuclei to form a heavier, more stable nucleus

stars produce their energy this way Currently __________________ are

necessary in order to initiate fusion possible future energy source

high temperatures

4 H + 2e He + energy 1

1

1

0

2

4

Page 34: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Fusion – two nuclei combine to form a heavier nucleus.

FUSION: two nuclei combine to form a heavier nuclei

Page 35: CHEMISTRY 1 CHEMISTRY 1 Nuclear Chemistry Chapter 28.

Proton-proton chain reaction

Fusion reaction in our Sun’s core.

Proton-proton chain reaction