Nuclear Chemistry

The Atom

The atom consists of two parts:

1. The nucleus which contains:

2. Orbiting electrons.

protonsneutrons

XA

Z

Mass number

Atomic number

Element symbol

= number of protons + number of neutrons

= number of protons

U235

92U

238

92

There are many types of uranium:

Mass #

Atomic #

Number of protons

Number of neutrons

Mass #

Atomic #

Number of protons

Number of neutrons

235

92

92

143 146

92

92

238

Same number of protons but different number of neutrons is

an…..

ISOTOPE

Most naturally occurring isotopes are stable.

Atoms want to be stable

Determined by ratio of p+ to n0

Nucleus Stability

Radioactive Decay(radioactivity)

Unstable nuclei decomposes into stable nuclei

Half- Life is the time it takes for this decay to occur.

Click Link to View Video:https://www.dropbox.com/s/0c380hppk60ikz1/Nuclear%20Half%20Life_%20Calculations.mp4?dl=0

Half Life:Time for half of the radioactive nuclide to decay

1. How much of a 100. g sample of 198Au is left over 8.10 days if its half-life is 2.70 days?

2. A 50.0 g sample of 16N decays to 12.5 g in 14.4 seconds. What is the half-life?

3. The half life of 42K is 12.4 hours. How much of a 750g sample is left over after 62.0 hours?

4. What is the half-life of 99Tc if a 500 g sample decays to 62.5g in 639, 000 years?

5. There are 5.0 g of Iodine -131 left after 40.35 days. How many grams were in the original sample if its half-life is 8.07 days?

• an alpha particle (a),

• a beta particle (b),

• or a gamma ray( ).g

Radioactive Decay emits:

When an unstable atom creates an alpha particle.

Alpha particle is identical to that of a helium nucleus. It contains two protons and two neutrons.

Alpha Decay

He4

2

Alpha Decay

Ra226

88

Rn222

86

He4

2

XA

ZY

A - 4

Z - 2+ He

4

2

Alpha Decay

unstable atom

more stable atom

alpha particle

Alpha Decay

Ra226

88+ He

4

2Th

230

90

U234

92Th

230

90+ He

4

2

+Pb214

82He

4

2Po

218

84

Beta Decay

Beta particle is a fast moving electron created when a n0 changes into a p+ & e-

When an unstable atom creates a beta particle.

Beta Decay

Po218

84

b0

-1

At218

85

XA

ZY

A

Z + 1+ b

0

-1

Beta Decay

unstable atom

more stable atom

beta particle

Beta Decay

Bi210

83 Po210

84+ b

0

-1

Pb210

82Tl210

81+ b

0

-1

Pa234

91Th

234

90+ b

0

-1

Gamma Decay

• Not a charged particle it is energy, it’s a photon.

• Electromagnetic radiation with high frequency

Draw the correct wave

Symbol Composition Range ShieldAlpha Particle

 He or α

Helium nucleus

Beta Particle Gamma Ray

short Paper, skin

Symbol Composition Range ShieldAlpha Particle

 He or α

Helium nucleus

Beta Particle

e- or β

Electron

Gamma Ray

short Paper, skin

Heavy Clothing, glass, light metals, plastic

Symbol Composition Range ShieldAlpha Particle

 He or α

Heliumnucleus

Beta Particle

e- or β

Electron

Gamma Ray

Photons (electromagnetic spectrum)

short Paper, skin

Heavy Clothing, glass, light metals, plastic

Long Lead or concrete