Chemistry 101:Chemistry 101:NuclearNuclear

By the Illustrious By the Illustrious

Kenny Chan and Johnny Kenny Chan and Johnny MospanMospan

Decay ParticlesDecay Particles

Alpha Particles (α) – He-2Alpha Particles (α) – He-2 Beta Particles (β) - e-Beta Particles (β) - e- Photon Particles (γ)Photon Particles (γ)

Alpha DecaysAlpha Decays

U-238 → He-4 + ___?U-238 → He-4 + ___? The # of protons and mass must be The # of protons and mass must be

equal on both sides.equal on both sides. Therefore, the unknown must have Therefore, the unknown must have

90 protons90 protons And since Uranium has a mass of 238 And since Uranium has a mass of 238

and Helium has a mass of 4, the and Helium has a mass of 4, the unknown has a mass of 234.unknown has a mass of 234.

Alpha Decays (cont.)Alpha Decays (cont.)

U-238 → He-4 + ___?U-238 → He-4 + ___? Well, the unknown is Th-90Well, the unknown is Th-90 U-92 → He-2 + Th-90U-92 → He-2 + Th-90

Beta DecaysBeta Decays

Th-91 → β + ____?Th-91 → β + ____? Same logic as before. Thus, 91 protons Same logic as before. Thus, 91 protons

for the unknown.for the unknown. Furthermore, since Thallium has a Furthermore, since Thallium has a

mass of 234 and a Beta particle has a mass of 234 and a Beta particle has a mass of 0, then the unknown has a mass of 0, then the unknown has a mass of 234.mass of 234.

The unknown is Pa-234The unknown is Pa-234 Th-91 → β + Pa-234Th-91 → β + Pa-234

Positron EmissionPositron Emission

A positron is a nuclear particle A positron is a nuclear particle having the same mass as an electron having the same mass as an electron but a positive charge.but a positive charge.

Same concept as Beta decays, Same concept as Beta decays, except the Beta particle has a charge except the Beta particle has a charge of 1+ instead of 1-of 1+ instead of 1-

Positron Emission (cont.)Positron Emission (cont.)

Po-207 → β (1+) + ____?Po-207 → β (1+) + ____? Same logic as before.Same logic as before. Since Polonium has 84 protons, the Since Polonium has 84 protons, the

unknown must have 83 protons.unknown must have 83 protons. Mass of unknown must be 207Mass of unknown must be 207 The unknown is Bi-207The unknown is Bi-207 Po-207 → β (1+) + Bi-207Po-207 → β (1+) + Bi-207

e- Capturee- Capture

It’s basically the opposite of a Beta It’s basically the opposite of a Beta decaydecay

Put the Beta particle on the reactants Put the Beta particle on the reactants side instead of on the products sideside instead of on the products side

Be-7 + β → ____?Be-7 + β → ____? Same logic as before.Same logic as before. Unknown must have 3 protons.Unknown must have 3 protons. Unknown must have a mass of 7Unknown must have a mass of 7 Be-7 + β → Li-7Be-7 + β → Li-7

More Decay StuffMore Decay Stuff

Johnny’s an idiot and can’t scan stuff.Johnny’s an idiot and can’t scan stuff. Johnny’s also lazy.Johnny’s also lazy. See board for picture.See board for picture.

Mass DefectMass Defect

Given:Given: H-1 + n-1 → H-2H-1 + n-1 → H-2 H-1 = 1.004552gH-1 = 1.004552g n-1 = 1.008665gn-1 = 1.008665g H-2 = 2.01410gH-2 = 2.01410g Find Change in Energy. Find Change in Energy.

Mass Defect (cont.)Mass Defect (cont.)

∑ ∑ mass (final) - ∑ mass (initial) = Δmmass (final) - ∑ mass (initial) = Δm (2.01410) – (1.007825 + 1.008665) = Δm(2.01410) – (1.007825 + 1.008665) = Δm Δm = -0.00239 g/molΔm = -0.00239 g/mol E = (Δm) c^2E = (Δm) c^2 C (speed of light… aka “Johnny’s C (speed of light… aka “Johnny’s

constant) = 2.9979 * 10^8constant) = 2.9979 * 10^8 E = (0.00239)(3*10^8) = 2.15*10^8 E = (0.00239)(3*10^8) = 2.15*10^8

J/molJ/mol

Mass Defect (cont.)Mass Defect (cont.)

In fusion, mass defect is associated In fusion, mass defect is associated with binding energywith binding energy

Fusion is putting things together to Fusion is putting things together to form one productform one product

In fission, mass defect is associated In fission, mass defect is associated with kinetic energy of product particlewith kinetic energy of product particle

Fission is splitting things apart from Fission is splitting things apart from one reactantone reactant

Rate of Nuclear DecaysRate of Nuclear Decays

A = Activity = decays/timeA = Activity = decays/time A = kNA = kN Derive equation for Number of Derive equation for Number of

Decays at time T (see board!)Decays at time T (see board!)

Half-Life StuffHalf-Life Stuff

At half-life, 2N = NoAt half-life, 2N = No Derive equation for half-life…Derive equation for half-life… (see board!)(see board!)

Predicting DecaysPredicting Decays

Once again, see the board.Once again, see the board.

The End.The End.

Mospan and Chan Mospan and Chan 1, Chemistry 01, Chemistry 0