Three Mile Island1979

Chernobyl1986

Yankee Nuclear Plant, Vermont—same type as theFukushima plant.

Nuclear Chemistry involves changes in the nucleus.When the nucleus of one element is changed into the nucleus of another element, it is called transmutation. The nucleus is said to decay or disintegrate (fall apart).

I.Nuclei contain neutrons n and protons pamu = atomic mass unit ≈ mass of 1 n or 1 pThe masses of electrons are ignored.

mass (amu) charge symbolproton 1 +1 or

neutron 1 0

electron 0 -1

H11 p1

1

n01

e-10

C612

isotopedifferent ways of

writing the symbols# of p # of n

C-12

C-14

carbon-12

carbon-14

Ex. Isotopes – same atomic # (same # of p) different mass # (different # of

n)

The symbol for any particle X is:

XZ

A

atomic # = # of p = + charge in nucleus

mass # = #p + #n

C614

Each unique nucleus is called a nuclide.

C12

C14

6 6

6 8

Americium-241

II. An isotope that is unstable is called a

radioisotope. Radioisotopes emit (give off)

energy in the form of particles as they decay (change)

into new nuclei. They are said to be radioactive,

and the decay is called radioactivity.

Stable nuclei do not decay.

A. For smaller nuclei, the #p ≈ #n

B. For larger nuclei, the #n > # p because you need

more n’s to help hold the nucleus together.

C. Most elements have both stable and unstable

nuclei. Above bismuth (#p = 83), all the isotopes

of all elements are radioactive.

Smallernuclidestend to have the#n ≈ #p.

Ex:

F919

Biggernuclidestend to have the#n ≈ 1.5 #p.

Ex:

Pb82

208

#p = #n =

#p = #n =

910

82

126

III. When nuclei decay, they emit 3 basic types of radiation (or particles).

1.

2a.

2b.

3.

The research focused on detecting the presence of strontium-90, a cancer-causing radioactive isotope created by the more than 400 atomic tests conducted above ground that is absorbed from water and dairy products into the bones and teeth given its chemical similarity to calcium. The team sent collection forms to schools in the St. Louis, Missouri area, hoping to gather 50,000 teeth each year.[1] Ultimately, the project collected over 300,000 teeth from children of various ages before the project was ended in 1970.Preliminary results published by the team in the November 24, 1961, edition of the journal Science showed that levels of strontium 90 in children had risen steadily in children born in the 1950s, with those born later showing the most increased levels.[2] The results of a more comprehensive study of the elements found in the teeth collected showed that children born after 1963 had levels of strontium 90 in their baby teeth that was 50 times higher than that found in children born before the advent of large-scale atomic testing

The baby tooth survey:

Radiation can be separated into different types by passing neared charged plates. Negatively charged particles are deflected towards the positive plate, and positive particles towards the negative plate.

Why are gamma rays not affected?

Where would positrons end up on the plate?

Alpha () particles have the most charge and mass. They interact most with matter by ionizing it. This slows them, and they are the most easily stopped. Beta () particles can be stopped by a sheet ofaluminum. Gamma () radiation has the most penetrating power.High density materials like lead are required to stop it.

Pretend you are given three radioactive cookies—one alpha, one beta and the other, gamma. Pretend that you must eat one, hold the other in your hand, and put the other in your pocket. Which would you eat, hold and pocket, if you are trying to minimize your exposure to radiation?

Hold the alpha—your skin will protect you.Pocket the beta, your clothing likely will shield you.Eat the gamma, it will penetrate your body nomatter what you do with it.

Only one of two peopleto win two Nobel Prizes in 2 fields:1.Physics 1903 for her work on radiation

2.Chemistry 1911 for discoveringradium and polonium

The year 2011 has been declared the Year of Marie Curie by France and Poland.

1. Alpha Decay is the emission of an alpha () particle:

a/ It is a He nucleus.

b/ It contains 2 p and 2 n.

charge: +2 mass: 4 amu

c/ It is most often emitted by heavier nuclei.

Ex. The decay of Ra-226 into Rn-222 occurs

naturally because Ra-226 is radioactive.

decays

into

All nuclear equations, like the one given above,must be balanced—just like chemical equations.

Ra88

226 Rn86

222+ He

2

4

Conservation of mass: No mass is lost.

Total mass before decay = Total mass after decay Mass numbers (superscripts) must add up:

= +

Conservation of charge: No charge is lost.

Total charge before decay = Total charge after decay Atomic numbers (subscripts) must add up:

= +

226 222 4

88 86 2

The Radium Girls (1917):They painted watches with “glow in the dark” radium. The women, who had been told the paint was harmless, ingested deadly amounts of radium by licking their paintbrushes to sharpen them; some also painted their fingernails with the glowing substance.

2a. Beta Decay is the emission of a beta () particle:

a/ It is exactly the same as an electron

charge: -1 mass: 1/1800 amu ≈ 0

b/ The electron is emitted from the nucleus when

a neutron decays into a proton and an electron:.

n0

1 p1

1+ e

-1

0

Ex. Pb-214 decays into Bi-214

Pb82

214 Bi83

214+ e

-1

0

Conservation of mass:The mass of the electron is ignored because it

is so small compared to the n and p masses.mass numbers add up:

= +

Conservation of charge:atomic numbers (subscripts) must add up:

= +

214 214 0

82 83 -1

Google imagesof depleted uranium:

Normal uranium:99.3 % U-238.7 % U-235is separated so thatonly about .4%U-235 remains.

2b. Positron emission from the nucleus occurs when

a proton decays into a neutron and a positron (+):

A + is a positive electron. It is an example

of antimatter. It has

a/ the same mass as an electron, but

b/ opposite charge (same charge as a proton)

charge: +1 mass: 1/1800 amu ≈ 0

Ex. Potassium K-37 decays into argon Ar-37

p1

1 n0

1+ e

+1

0

K19

37 Ar18

37 + e+1

0

Conservation of mass:Like the electron, mass of the positron is ignored .

The mass numbers add up:

= +

Conservation of charge:atomic numbers (subscripts) must add up:

= +

Positrons and electrons annihilate each other (their

matter is transformed into energy) if they collide.

K19

37 Ar18

37 + e+1

0

37 37 0

19 18 +1

3. Gamma () radiation is also called rays.

They are high-energy particles of light.

a/ When or radiation is emitted, the nucleus is

often left in an excited state. It can move to a

lower and more stable state by emitting rays.

(This is similar to how atoms emit visible light

when electrons move to lower energy levels.)

b/ They have no charge and no mass.

symbol:

rays are not always shown in nuclear reactions

in Regents Chemistry.

0

0