Radioactive Isotope

Isotope which is unstable. It emits radiation &

changes into another kind of atom.

Transmutation Reaction

When one kind of nucleus changes into another kind

of nucleus.

Relationship between stability and energy

As stability , energy .

Stability

Depends on neutron to proton ratio.

Which elements are unstable?

All the elements with atomic number > 83 (or

beyond Bismuth)

Types of Radiation

Alpha, Beta, GammaSeparated by electric or

magnetic fields.

Least penetration power

Alpha radiation. Shielding can be paper or cloth.

Most penetration power

Gamma radiation. Requires lead/concrete

shielding.

2He or 2

Symbol for alpha radiation

4 4

2He or 2

Same as the nucleus of a helium atom

4 4

2He or 2

Mass = 4 amuCharge = +2

4 4

-1e or -1 or - or

Symbol for beta particle

0 0

-1e or -1 or - or

Fast moving electron originating from nucleus

0 0

-1e or -1 or - or

Mass = “zero”Charge = -1

0 0

+1e or +1 or +

Symbol for positron.

0 0

+1e or +1 or +

Mass = “zero.”Charge = +1.

Positive electron

0 0

0 or

Symbol for gamma radiation.

0

0 or

0 mass0 charge

0

0n or n

Symbol for neutron

1

1H or 1p

Symbol for proton

1 1

Alpha Decay

Unstable nucleus emits an alpha particle.

Atomic # by 2. Mass # by 4.

220Fr 4 + 216At

Unstable nucleus emits an alpha particle.

Atomic # by 2. Mass # by 4.

87 2 85

220Fr 4 + 216At

Equation represents natural transmutation. 1 term on reactant side.

87 2 85

220Fr 4 + 216At

Balance nuclear equations using conservation of

atomic number & conservation of mass

number.

87 2 85

4 + 216=220

87 = 2 + 85

# of Half-Lives

Elapsed timeLength of H.L.

Half-Life Map

Mass Elapsed Time

Fraction Remainin

g

# of Half Lives

Start mass

0 1 0

1 X H.L. ½ 1

2 X H.L. ¼ 2

3 X H.L. 1/8 3

4 X H.L. 1/16 4

Decay Mode

Same as type of particle emitted

Average Atomic Mass

Weighted average of the masses of the naturally

occurring isotopes.

Artificial Transmutation

Particle “bullet” hits target nucleus & new isotope is produced.

2 terms on reactant side.

Artificial Transmutation

32S + 1n 32P + 1H16 0 15 1

bullettarget

Artificial Transmutation

Particle “bullet” may be proton or alpha particle. To react with a nucleus, must overcome + + repulsive forces by accelerating bullet to high speeds.Particle “bullet” may be a neutron. Neutrons have no charge, so no repulsive forces to overcome. No acceleration necessary.

Fission

Fission is division.

Large nucleus (U-235 or Pu-239) is split into 2 medium sized nuclei by a neutron bullet. Excess neutrons & a great deal of energy are also produced.

239Pu + 1n 90Sr + 147Ba + 3 1n

Fission

94 0 038 56

Fusion

Fusion: U for unite and U for sun.

Very small nuclei (H & He) are jammed together. Huge amounts of energy are released.

1H + 2H 3He

Fusion

1 1 2

Identify each of the rxns

a) 1n + 235U 142Ba + 91Kr + 3 1n + energy

b) 59Co + 1n 60Co

c) 3He + 1H 4He + 0e

d) 14C 14N + 0e

0 92 56 36 0

27 0 27

2 1 2 +1

6 7 -1

fission

Artificial transmutation

fusion

Natural transmutation