nuclear chemistry chem 2124 – general chemistry ii alfred state college professor bensley

Nuclear Chemistry

CHEM 2124 – General Chemistry II

Alfred State College

Professor Bensley

Learning Objectives Learn the nuclear symbols for various

radioactive particles and forms of energy. Write a nuclear equation including deducing

the reactant or product of said reactions. List and predict the various types of

radioactive decay. Determine the product nucleus in

bombardment reactions. State the purposes of a Geiger counter.

Learning Objectives Define the radioactive decay constant. Define half-life and calculate half-life from

the decay constant. State the ways in which radioactive isotopes

are used for chemical analysis. Describe how isotopes are used for medical

therapy and diagnosis. Explain the difference between nuclear

fusion and nuclear fission reactions and describe applications of each.

Nuclear ChemistryI. Introduction

A. Isotopes (Review)

B. Radioisotopes

C. Types of Radiation1. Alpha Particle2. Beta Particle3. Gamma Rays4. Positrons

Nuclear Chemistry

Nuclear Chemistry

II. Half Life (t1/2) - the time it takes for one-half of a radioactive sample to decay

Table 10.2

Radioactive Decay of a 1.000-g Sample of Iodine-131

Nuclear Chemistry

– Mathematical relationship to use when calculating half lives or amount of material left after x half-lives have passed.

– Based on natural logarithms (ln)– K = elimination rate constant = -0.693

M/M0 = e-KT/t1/2

ln(M/M0) = -KT/t1/2

A. Decay Curves

Examples 1 and 2

A radioactive substance has a half-life of 7.5 minutes. If you initially have 100 grams of this material, what mass would remain after one hour?

You have a sample of radioactive material that initially weighs 50 grams now weighs only 12.75 grams after 24 hours. What is the half-life of this substance?

Nuclear Chemistry

III. Health Effects of RadioactivityA. Nuclear radiation will damage or kill rapidly

dividing cells such as bone marrow, skin, and the reproductive and intestinal systems.B. Food is irradiated, exposed to gamma

radiation, to kill any living organism in the food.

Nuclear Chemistry

original nucleus

newnucleus

+ radiationemitted

IV. Nuclear ReactionsA. Radioactive decay

B. Nuclear Equations

C. Alpha Emission (Decay) - decay of a nucleus by emitting an particle

Nuclear Chemistry

D. Beta Emission (Decay) - decay of a nucleus by emitting a βparticle; 1 neutron is lost and 1 proton is gained.

Nuclear ChemistryE. Positron Emission (Decay) - decay of a nucleus

by emitting a positron, β+; 1 proton is lost and 1 neutron is gained.

Nuclear Chemistry

99m43 Tc +99

43 Tc

F. Gamma Emission (Decay) - decay of a nucleus

by emitting radiation.

Commonly, emission accompanies or β emission.

Nuclear Chemistry

G. Nuclear fusion - the joining together of two light nuclei to form a larger nucleus.

2

1H +

3

1H

4

2He

1

0n+

Nuclear ChemistryH. Nuclear fission is the splitting apart of a heavy

nucleus into lighter nuclei and neutrons. It can begin when a neutron bombards a uranium-235 nucleus:

23592 U + 1

0n

91

36 Kr +142

56 Ba + 10

n3

Example 3

Complete the following nuclear reactions by filling in the boxes with the appropriate numbers or symbols:

1. 238Pu 234 U + 2. 14C 14N +

3. 238U + 0e 4. 11B 7Li +

92 -1 5 3

5. 85Kr 85Rb + 36 37

Examples 4 and 5

Write a balanced equation for the β-decay of Phosphorus-32, a radioisotope used to treat leukemia and other disorders.

Write a balanced equation for the positron emission of fluorine-18, a radioisotope used for imaging in PET scans.

Technetium-99m

Figure 10.5

23

Focus on Health and MedicineRadioisotopes Used in Treatment

PET Scan showing Reduced Enzyme Levels in Various Body Areas of a Smoker

Nuclear ChemistryV. Modern Nuclear Reactors (Fission)

A. Chernobyl (1986)

Aerial Picture of Reactor at Chernobyl Following Nuclear Accident in 1986

Chernobyl - 2006 Interesting Facts

Nuclear Chemistry

B. Three Mile Island (3/28/1979)

Nuclear ChemistryC. Fukushima Daiichi (2011)

D. Modern Nuclear Warheads

Top – Downtown Nagasaki prior to August, 1945

Bottom – Same Area of Downtown Nagasaki After Atomic Bomb was Dropped