nuclear chemistry. reactions chemical involve electrons affected external factors (temp, pressure,...
TRANSCRIPT
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