nuclear chemistry bravo – 15,000 kilotons. nuclear symbols element symbol mass number (p + + n o )...

Nuclear ChemistryBravo 15,000 kilotons

Nuclear SymbolsElement symbolMass number (p+ + no)Atomic number(number of p+)

Types of Radioactive Decayalpha production (a): helium nucleus

beta production (b): neutron splits into an electron and a proton2+

CREATING A REACTION (-particle)On either side of the arrow, the mass number and atomic number MUST be the same (alpha-particle is always a helium nucleus)238U 4He + 234Th 92 2 90

On the left side, mass number is 238On the right side, 234 + 4 = 238On the left side, the atomic number is 92On the right side, 90 +2 = 92

CREATING A REACTION (-particle)Both sides of the reaction still need to balance.In beta-radiation, a neutron splits apart to form an electron and a proton234Th + 234Pa 0e 90 91 -1On the left side, mass number is 234On the right side, 234 + 0 = 234On the left side, the atomic number is 90On the right side, 91 - 1 = 90

Alpha RadiationLimited to VERY large nucleii.

Beta RadiationConverts a neutron into a proton.

PRACTICEEach of the following compounds emits an alpha particle, write the balanced nuclear reaction

222Ra 88

208Po 84

PRACTICEEach of the following compounds emits a beta particle, write the balanced nuclear reaction

14C 6

131I 53

Types of Radioactive Decaygamma ray production (g):

positron production:

electron capture: (inner-orbital electron is captured by the nucleus)

GAMMA RADIATIONGamma radiation does not produce any particles by itselfIt is tied to another radioactive decayBecause the release of radioactive particles frees some energy in the nucleus, this energy takes the form of gamma radiationThere is a lot of energy holding the nucleus together so gamma radiation has a LOT of energy

Positron and Electron capturePositron emissions occur when a proton splits apart into a neutron and an electronTherefore the mass number does not change, but the atomic number changes the element into something newElectron capture occurs when a proton captures one of the inner valence electrons and converts it into a neutronThis causes the release of a powerful neutrino (as powerful as gamma radiation)

TRY THESEThe following go through a positron emission. Write the balanced reaction:

17F 9

31S 16

TRY THESEThe following go through an electron capture. Write a balanced equation.

76Kr 36

125I 53

ANOTHER WAY TO SYMBOLIZE ISOTOPESSo far we have seen one way to symbolize isotopes:17F 9

31S 16Since we know the number of protons, we can symbolize the isotope with just the mass number:Fluorine-17Sulphur-31

Types of Radiation

Deflection of Decay ParticlesOpposite charges_________ each other.Like charges_________ each other.attractrepel

NuclearStabilityDecay will occur in such a way as to return a nucleus to the band (line) of stability.

HALF LIFEWhen an isotope goes through a radioactive emission, it does so at a fairly constant rateScientists use this property to date items

Half-life: The time it takes for of a radioactive isotope to decay to a stable formExample: Carbon-14 has a half life of 5730 yearsIt takes 5730 years for of radioactive Carbon-14 to decay to the stable form or Nitrogen-1414C 0e + 14N 6 -1 7

Half-life Concept

HOW TO SOLVE HALF-LIFEIodine-131 is used to destroy thyroid tissue in an over-productive thyroid gland. The half-life of iodine-131 is 8 days. If a hospital received a shipment of 200g of iodine-131, how much iodine-131 would remain after 32 days?

SOLUTIONStep 1: Find out how many -lives have occurred(32 days/8 days for half-lives)4 half-livesStep 2: Four each half-life, divide the sample by 24 half lives = x x x = 1/16Step 3: Divide the initial sample size200g/16 = 12.5g will remain

TRY THISMercury-197 is used for kidney scans and has a half-life of 3 days. If the 32g of mercury-197 is ordered, but takes 15 days to arrive, how much would arrive with the shipment?

Sample Half-Lives

A Decay SeriesA radioactive nucleus reaches a stable state by a series of steps

Nuclear Fission and FusionFusion: Combining two light nuclei to form a heavier, more stable nucleus.

Fission: Splitting a heavy nucleus into two nuclei with smaller mass numbers.

Energy and MassNuclear changes occur with small but measurable losses of mass. The lost mass is called the mass defect, and is converted to energy according to Einsteins equation:DE = Dmc2 Dm = mass defect DE = change in energy c = speed of lightBecause c2 is so large, even small amounts of mass are converted to enormous amount of energy.

Fission

Fission ProcessesA self-sustaining fission process is called a chain reaction.

Event

Neutrons Causing Fission

Result

subcritical

< 1

reaction stops

critical

= 1

sustained reaction

supercritical

> 1

violent explosion

A Fission Reactor

Fusion

MORE PRACTICE PROBLEMSNitrogen-13 emits beta radiation and decays to Carbon-13. This has a half-life of 10 minutes. You start with 2.0g of Nitrogen-13:Write out the balanced nuclear reaction.Calculate how much nitrogen-13 is remaining after 40 minutes.

MORE PRACTICE PROBLEMSManganese-56 decays with beta radiation and has a half-life of 2.6 hours. You begin with 1mg of Manganese-56:Write the balanced nuclear reaction.How much manganese-56 is left after 10.4 hours?