Chm115 s15 Lecture7 Pvr

Daily Page: Tuesday, February 03, 2015

LEARNING OBJECTIVES

Know that the mass of a nuclide

is less than the sum of its

nucleons masses (mass defect).

Know that mass difference

contributes to nuclear stability;

relate it to nuclear binding energy

per nucleon.

How unstable nuclides undergo

either fission or fusion to increase

their binding energy per nucleon.

The current application of fission

and potential application of fusion

to produce energy.

Nuclear chemistry in Health

(Nuclear Medicine)

ASSIGNMENTS

CONNECT Homework:

HW03 due Thurs., Feb. 05

HW04 due Tues., Feb. 10

**material covered on Exam-1

(2/12/15, 6:30 PM)**

Next Lecture

Atomic Structure

Reading for Thursday: Textbook sections 7.1, 7.2, 7.4

Laboratory

Titrations and accuracy of

glassware (Chapter 4)

From Last Class

Application of

Carbon Dating

50 mg piece of the

linen revealed it to

be from 1260-1390

AD

k = ln 2 / t or t = ln 2 / k ln{No/N} = kt ln{[Ao]/[A]} = kt

t = ln{No/N} / k

Band of Stability; n/p ratio to determine - and +decay or electron capture;

Atomic number >83: -decay

Mass defect

Mass of nuclide is not equal to the sum of the

masses of individual nucleons in the nuclide.

7 11H + 7

10n

147N

14.11543 amu 14.0031 amu

(Mass of a proton = 1.007825 amu; and of a neutron = 1.008665 amu)

The mass defect (mass) is equated to the energy

required to hold the nuclear particles together.

The 147N nuclide is missing 0.1123 amu. This is

known as the mass defect.

E = mc2 or E = mc2

E = energy (in J)

produced when mass m is converted into energy

or consumed when energy is converted to mass

m = mass in kg (1 amu = 1.6605 x 1027 kg)

c = speed of light (2.9978 x 108 m s-1)

147N 7

11H + 7

10n E = N. B. E.

Nuclear Binding Energy = Energy required to

separate nucleus of atom into protons and

neutrons OR the energy holding it all together

Question # 1

a. 1.0 x 1016 J

b. 3.4 x 107 J

c. 1.7 x 10-11 J

d. 5.6 x 10-20 J

What is the N.B.E of 147N per nuclide?

147N 7

11H + 7

10n E = N. B. E.

m = 0.1123 amu

1 amu = 1.66 x 1027 kg; c = 3.00 x 108 m s-1

m = 0.1123 amu x 1.66 x 10-27 kg/1 amu

= 1.86 x 10-28 kg

N.B.E. = 1.7 x 10-11 J/nuclide

E = 1.86 x 10-28 kg x (3.00 x 108 m s-1)2

= 1.68 x 10-11 kg m2 s-2 = 1.68 x 10-11 J

Question # 2 (1 pt quiz)

a. 6.0 x 1039 J

b. 3.3 x 104 J

c. 1.0 x 1013 J

d. 5.6 x 10-17 J

e. 1.0x 1034 J

N.B.E of 147N per nuclide is 1.68 x 10-11 J

What is the N.B.E of 147N per mole?

1.68 x 10-11 J/nuclide x 6.022 x 1023 nuclide/mol

(Avogadro constant)

N.B.E./mol = 1.0 x 1013 J/mol (1.0x1010 KJ/mol)

Energy of Nuclear Vs Chemical reactions

Nuclear Binding Energy: the energy required to

convert a nucleus to protons and neutrons.

Chemical Reaction: Small changes in energy

Nuclear Reaction: Large Changes in energy

2 Al + Fe2O3 2 Fe + Al2O3 E 1 x 103 kJ/mol

CH4 + 2O2 CO2 + 2H2O E 802 kJ/mol

14

7N 7 11H + 7

10n E = 1.0 x 10

10 kJ/mol

N.B.E. is usually expressed in eV or MeV

14

7N 7 11H + 7

10n

14.0031 amu 14.11543 amu

N. B. E of 14N per nuclide is 1.68 x 10-11 J

1eV = 1.602x10-19 J; 1 MeV = 1.602x10-13 J

(1 amu = 931.5x106 eV = 931.5 MeV)

Thus, N. B. E of 14N (0.1123 amu) = 105 MeV/nuclide

NBE/nucleon of 14N is105/14 = 7.5 MeV/nucleon.

NBE/nucleon of 12C is 92.16/12 = 7.680 MeV

Nuclear Binding Energy in eV

The greater the binding energy per nucleon, the more stable

the nucleus. B.E. per nucleon maximizes around 56Fe.

These are the most stable nuclei.

Binding Energy per Nucleon


Atomic mass: >56, nuclei split

(fission) into lighter nuclei.

238U + 1on 87Br + 146La + 3 1on

More BE/nucleon

atomic mass:

Nuclear Reactions - Fission

Fission: production of lighter nuclei by the

decomposition of a heavier nucleus. Often, but not

always, produced when a heavier nucleus is

bombarded with a neutron.

One of many examples in a nuclear reactor

23592U +

10n -->

8735Br +

14657La + 3

10n

Manufacture of tritium

63Li +

10n

42He +

31H

In what way is nuclear fission different from radioactive decay?

Nuclear Fission: The Initiation Reaction

http://www.youtube.com/watch?v=3HtokHufQSI&feature=related
http://www.youtube.com/watch?v=3HtokHufQSI&feature=related

Propagation

Controlled Propagation/Termination

Question #3 (1 pt quiz)

Identify element X in the following nuclear reaction.

235U + 10n 143Xe + X + 3 10n

a) 92Sr

b) 90Sr

c) 89Sr

d) 92Kr

e) 90Kr

Nuclear Chemistry and Energy

17

Generating Electricity

A Boiling Water Nuclear Power Reactor

Supporting structure

Pressure vessel

Shielding/containment

Fuel Assemblies

Moderator (D2O)

Control rods (B or Cd)

Coolant

Nuclear Power Station

Why didnt these reactors explode like an atomic bomb?

Nuclear fuel: 3% U-235

Weapon grade uranium: 97% U-235

Different design and geometries

Nuclear Reactions - Fusion

Fusion: Production of a heavier nucleus by combination of

lighter nuclei.

21H +

31H

42He +

10n + 1.7x10

9 kJ/mol

63Li +

10n

31H +

42He Source of tritium?

The greater the binding energy per nucleon, the more stable

the nucleus. B.E. per nucleon maximizes around 56Fe.

These are the most stable nuclei.


Question #4

Is this reaction

11H +

11H

21H +

01e (+)

a. Fusion

b. Fission

c. Neutron capture

d. Beta decay

Energy Calculation

How much energy per mole of 21H produced? 11H +

10n

21H

11H = 1.007825 amu

21H = 2.01410 amu

10n = 1.008665 amu

1 amu = 1.6605 x 10-27 kg c = 3.00 x 108 m/s

m = 2.01410 g - (1.007825 g + 1.008665 g)

= -0.00239 g

E = -0.00239 g x 1 kg/1000g x (3.00 x 108 m/s)2

= -2.15 x 1011 kg m2 / s2 = -2.15 x 1011 J

(note the change in the sign)

Nuclear Reactions - Neutron Capture

Neutron capture builds heavier

isotopes. Plutonium forms in a series of reactions

several of which involve neutron capture. 238

92U + 1

0n 239

92U

23992U

23993Np +

01e (

-)

23993Np 239

94Pu + 0

1e (-)

23994Pu +

10n

24094Pu

24094Pu +

10n

24194Pu

Neutron capture: capture of a neutron by a nucleus

giving an isotope with a mass number one unit

higher.

Nuclear Reactions - Neutron Capture

Other neutron capture events involving

plutonium lead to new nuclides.

23994Pu +

10n

24095Am +

0-1e

Smoke Detectors

24195AmO2

42 + +

23793NpO2

Half-life = 432 years

particles ionize O2 and N2 in the ionization chamber.

A low-level electric voltage applied across the chamber is used

to collect these ions, causing a continuous small electric current

to flow between two electrodes.

When smoke enters, smoke particles attach to the charged ions,

neutralizing them. This causes the electric current to fall, setting

off the alarm.

Nuclear Medicine

Radionuclides are also administered to treat disease or provide pain relief.

Iodine-131 is often used for the treatment of thyrotoxicosis and thyroid cancer.

Prostate cancer: Permanent implantation of seeds of Pd-103 or I-125.

Pd-103, t1/2 = 16 days, x-ray energy 21 keV

I-125, t1/2 = 60 days, energy 30 keV

Ir-192 for high dose, t1/2 = 73.83 d ( and -emission)

Radionuclides for cancer

Pd produces a lower energy photon, higher energy transfer, larger radiobiological effect.

Implant 80-100 seeds Remain in patient

permanently.

103

Nuclear Reactions

Positron Emission, +-decay

+-decay: decay by loss of an a positron, a particle with the

same mass as an electron but with a positive charge (a

positive electron).

116C

115B +

01e

189F

188O +

01e

Positron emission is usually accompanied by the

subsequent appearance of two gamma rays that result

when the positron interacts with an electron, and the two

annihilate each other. All of their mass is converted into

energytwo 0.511MeV gamma rays are produced.

01e +

01e 2 (0.511 MeV each)

Question #6

189F t1/2 =109.771 min.)is prepared for use in

PET by bombarding a sample containing

glucose with protons. Which nuclide, X, in

the glucose combines with a proton to

produce 189F?

X + 1p 189F + 1n

a. 199F

b. 179F

c. 178O

d. 188O

PET

18O + 1p 18F + 1n 18F 18O + 1e

PET

Positron Emission Tomography

+ + - 2 (0.511 MeV each, in opposite

directions)

Summary

Nuclear reactions are different from chemical reactions

Atoms change identity

Energy scale different

Types of nuclear reactions

Balancing

Kinetics

First order process; half-life constant

Nuclear power plants use fission to produce energy

Know the components of a reactor and what they do

Definitions of fission and fusion.

The B.E. per nucleon is a guide to fusion or fission

Nuclear medicine

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Chm115 s15 Lecture7 Pvr