Nuclear Chemistry. Natural Radioactivity The spontaneous breakdown of atomic nuclei, accompanied by...

Nuclear Chemistry

Natural RadioactivityThe spontaneous breakdown of

atomic nuclei, accompanied by the release of some form of radiation

Transmutation: the conversion of one element to another by means of a nuclear changeTo detect Radioactivity one could use Geiger Counter

Types of Radioactive Emissions

All differ in mass, size and charge Reference Table O

Alpha Particle: 42

positive 2 chargehelium nucleusmass of 4amuEx: 226

88Ra 22286Rn + 4

2He

Beta Particle: 0-1

negative chargeacts like a high speed electronno mass

Example: 23592U 235

93Np + 0-1

Gamma Radiation (NOT a Particle) no chargeacts like a high speed x-ray but

with a lot more energyno mass

Positron Particle: 0+1

positive 1 chargeacts like positive electronsno mass

Particle Symbol Mass Charge Relative Penetrating Power

Alpha 42 4amu +2 Low

Beta 0-1 0 -1 Moderate

Gamma 00 0 0 High

Positron 0+1 0 +1 Moderate

Separation of Radioactive emissions by charge:

Positively Charged Plate Negatively Charged Plate

+ -

+ -

+ -

+ -

Half-Life The time it takes for half of the

atoms in a given sample of an element to decay.

Some selected half-lives are found on Table N

All reactions on Table N are Natural Transmutation

Formulas for half-life reactions are found on Table T

Artificial Radioactivity Artificial Transmutation: artificial

radioactivity produced by bombarding the nuclei of stable atoms with high energy particles, thereby producing radioactive atoms

Fission Reactions The splitting of an atomic nucleus

into two smaller nuclei by bombardment of a neutron (Nuclear Bomb). *Nuclear Reactors are fission reactors.

Example: 23592U + 1

0n 14256Ba + 191

36Kr + 3(1

0n) + Energy

Fusion Reactions A nuclear reaction in which two or

more light nuclei combine to form a single nucleus. Requires huge amounts of pressure and extremely high temperatures. Produces much more energy than fission. Occurs naturally on the sun. (H-bomb)

Example: 21H + 2

1H 42He + Energy

Uses of Radioactive Isotopes Lab: To trace chemical reactions.

Industry: Radiating food to preserve by killing bacteria, mold, insect eggs.

Medicine Must have relatively short half-

lives and be quickly eliminated from the body.

I-131 diagnosing and treating Thyroid conditions (half-life 8.07 days)

Co-60 emits large amounts of gamma radiation as it decays, these rays can be aimed at cancerous tumors (half-life 5.26 years)

Ra-226 used in treatment of certain cancers (half-life 1600 years)

Tc-99 used in diagnosis of brain tumors (half-life 2.13x105 years

GeologyFossils C-14 to C-12 ratio (while alive

they are in equal amounts, once an organism dies C-14 is no longer taken in).

Rocks U-238 to Pb-206 ratio (U-238 decays through a series of steps until it forms stable Pb-206. As time passes, the amount of U-238 decreases while the amount of Pb-206 increases).

Balancing Nuclear Equations Steps for Balancing:

Due to the Law of the Conservation of Matter, whatever is on the left side of the equation must also be on the right side of the equation.

Add the mass numbers on the left side of the equation, this MUST equal the total mass numbers of the right side of the equation.

Add the atomic numbers on the left side of the equation, this MUST equal the total atomic numbers on the right side of the equation.

Example: 3216S + 1

0n 11H + 32

15P