Chem 162-2011 Lecture 23-2

Chem 162-2011 Lecture 23-2 - CHEMISTRY 162-2011 LECTURE 23...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Chem 162-2011 Lecture 23 1 CHEMISTRY 162-2011 LECTURE 23 ANNOUNCEMENTS MISCELLANEOUS EXAMS Final exam, Monday, May 9 th , 12:00 - 3:00 PM - Chapters 12-19, 22.7-22.9 (or 20.7-20.9) Importance of final exam (Worth more than 220 points) - For borderline students: trend - For “A” students (borderline or not) - For all students whose score is 35% STUDY! STUDY! STUDY! - Stop part-time jobs, sports practicing, partying, etc. Urgent to prioritize review session topics, upon request by e-mail ATTENDANCE Sign in
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chem 162-2011 Lecture 23 2 PLAN FOR TODAY : CHAPTER 19 – NUCLEAR CHEMISTRY 19.1 Radioactivity and nuclear equations 19.2 Naturally occurring radioactivity 19.3 Radioactive decay rates 19.4 Synthetic nuclides 19.5 Transuranium elements 19.6 Nuclear stability
Background image of page 2
Chem 162-2011 Lecture 23 3 SELECTED EQUATIONS FOR NUCLEAR CHEMISTRY Radioactivity, or radioactive decay, is the spontaneous change of the nuclei of certain atoms, accompanied by the emission of subatomic particles and/or high-frequency electromeagnetic radiation. CAPTURED OR EMITTED PARTICLES/RAYS Alpha particles 4 2 α = 4 2 He Sum of protons and neutrons = mass number (neutrons and protons are nucleons) Beta particles *** β - = 0 -1 β = 0 -1 e Number of protons (or charge) = atomic number Gamma ray ** 0 0 γ Positron particle β + = 0 1 e Neutron 1 0 n Proton 1 1 H **Nuclei have energy levels just as electrons do. When a nucleus in an excited state drops to a lower energy level, the energy is released in the form of a gamma ray. Atoms that emit gamma rays are high energy and are identified with an asterisk. ***An electron can be emitted or captured. Capture: An inner core electron can “fall” into the nucleus to combine with a proton and form a neutron. 0 -1 e + 1 1 H 1 0 n. An outer shell electron then drops to fill the vacancy, releasing an X-ray. 125 53 I + 0 -1 e 125 52 Te + 0 0 γ RADIOACTIVE DECAY RATE Reaction Differential I n t e g r a t e d Order Rate Law rate law Half-life* 1 Rate = λ N l n ( N t /N o ) = - λ t t 1/2 = 0.693/ λ ** l n ( N t ) = - λ t + ln(N o ) Rate = rate of radioactive decay = activity (“A”) = disappearance of atoms/sample per second = disintegrations of atoms/sample per second = disintegrations per second = decays per second λ = the decay constant N = concentration in molarity, number of atoms/sample, molecules/sample, moles/sample, g/sample, %, emission counts/sample, rate of decay/sample Note similarity to equations from KINETICS chapter: KINETICS Reaction Differential I n t e g r a t e d Order Rate Law rate law Half-life* 1 Rate = k[A] ln(A t ) = -kt + ln(A o ) t 1/2 = 0.693/k * For a first order reaction, each successive half-life is equal to the preceding one. **Unlike chemical reactions, k is not dependent on T, or anything else. MASS DEFECT Calc. nuclear mass (= nucleon mass) = Actual nuclear mass + mass defect (Calc’d mass of neutrons + protons) (actual mass of nucleus) (binding energy) E = mc 2 J = kg x (3.00 x 10 8 ms -1 ) 2 or 931.5 MeV/u Units in 1 o reactions cancel, so are irrelevant.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
PERIODIC TABLE AND PERIODIC PROPERTIES
Background image of page 4
Chem 162-2011 Lecture 23 5 Atomic No. = Identification of element = No. of protons NATURE OF THE ATOM P+N P Li = 7 3 Li* + + + proton neutron electron nucleus _ _ _ LITHIUM Atomic No. = 3 = 3 protons
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 22

Chem 162-2011 Lecture 23-2 - CHEMISTRY 162-2011 LECTURE 23...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online