Nuclear Chemistry. Reactions Chemical Involve electrons Affected external factors (temp, pressure,...

Nuclear Chemistry

Reactions

Chemical• Involve electrons• Affected external

factors (temp, pressure, catalyst)

Nuclear• Involve the nucleus• Release WAY more

energy• Not affected by

external factors

Electrostatic force

• Interaction between charged particles• Opposite charges attract• Same charges repel

How does the nucleus stay together?

Strong Nuclear Force

• Attractive force that acts between all nuclear particles that are extremely close together• Keeps the nucleus together• Much stronger than electrostatic force!

Radiation

• The emission (and transmission) of energy through space in the form of waves

Radioactivity

Alpha α

Beta β

Gama γ

Neutron n

Proton p

42

0-1

00

10

11

Radioactive

• Any element that spontaneously emits radiation (shows signs of radioactivity)• Transmutation—changing of an atom’s nucleus such

that an new element is formed• Alpha, beta, and proton not neutron or gamma

• Transuranium elements

Why does an element go undergo transmutation?

• The stability of the nucleus depends on the neutron to proton ratio

• Unstable nuclei are found outside the band of stability

• If a nucleus is unstable, it will emit radiation (decay) to gain stability

Radioactive decay

• Unstable nuclei (those that can be found outside the band of stability) losing energy by emitting radiation in a spontaneous process

Radioisotope

• Isotopes of atoms with unstable nuclei and go through radioactive decay to obtain a more stable nuclei• Small nuclei—up to 20 protons usually stable• Exception: Carbon—14

• Large nuclei—tend to be radioactive, based on the ratio of protons to neutrons; ALL nuclei with 83 protons or more are radioactive

Nuclear Equations

• In a balanced nuclear equation, mass numbers and atomic numbers are conserved• Example• Electron capture

Th Ra + He230 90

226 88

42

Rb + e → Kr 0- 1

8137

8136

Vocab for Equations

Word Location in the equation

Bombardment Reactant

Capture Reactant

Decay Product

Emission (emit) Product

Reactant Product

Practice

1. Zr e + ?

2. Po He + ?

3. ? Rn + He

4. Ca e + ?

5. Cm He + ?

0-1

218 84

4 2

222 86

97 40

4 2

0-1

47 20

4 2

244 96

Half-life

• Time required for ½ of a radioisotope’s nuclei to decay into its products

• Equation: NT = N0 (1/2)n

NT =Amount remaining at time T N0 = initial amountn= number of half-lives

Practice

1. Scientists start with 50.0 g sample of a radioisotope. How much is left after four half-lives?

Practice

2. Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days?

Carbon-14 Dating

• Carbon-14 is evenly spread in Earth’s biosphere• Carbon-14 is

radioactive and undergoes beta decay; half-life of 5730 years• Dates carbon-bearing

materials us to 62,000 years

Practice