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Introduction to Atomic Structure and Nuclear Chemistry

Learn about the structure of atoms, isotopes, ions, and nuclear reactions. Explore the concepts of average atomic mass, half-life, alpha, beta, and gamma emissions, and nuclear fission and fusion.

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Introduction to Atomic Structure and Nuclear Chemistry

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  1. Happy Friday! • Please take out note packet and calculator

  2. The Atom

  3. The Atom protons, neutrons, and electrons • The atom is made up of ____________________________.

  4. PARTICLE SYMBOL MASS(amu) CHARGE Proton p 1.00 +1 Neutron n 1.00 0 Electron e-0 -1 • The proton and neutron have the same mass. • All of the mass of an atom comes from the nucleus.

  5. Atomic Number (Z) is the number of protons; this determines the identity of the element. • Mass Number (A) the sum of the protons and neutrons. (Round to a whole number). • Atomic Mass is the average mass of all the isotopes of the element.

  6. Al 13 14 (27-13) 13 19 K 19 20 82 Pb 82 125

  7. Nuclear Symbol Mass # 24 12 Mg 12 12 12 _______ p _______ n _______ e- Atomic # 25 30 25 55 _______ p _______ n _______ e- Mn 25 75 33 42 33 As _______ p _______ n _______ e- 33

  8. Ions • Cations • Anions ( + ions) are formed by removing electrons. ( - ions) are formed by adding electrons.

  9. Practice 20 20 18 40 20 +2 Ca _______ p _______ n _______ e- 56 +2 Fe 26 30 24 _______ p _______ n _______ e- 26 31 -3 P 18 15 16 _______ p _______ n _______ e- 15 - 80 35 36 Br 35 45 _______ p _______ n _______ e-

  10. Isotopes • Isotopes are different forms of the same element that have different numbers of neutrons, which gives a different mass. • Always add protons and neutrons to find the mass.

  11. Practice 6 6 6 12 6 C _______ p _______ n _______ e- 14 C 6 8 6 _______ p _______ n _______ e- 6

  12. Give the nuclear symbol for the particle with: 1. 50 protons, 50 electrons, and 70 neutrons 120 Sn 50 2. 47 protons, 46 electrons, and 63 neutrons 110 + Ag 47

  13. + 91 40 +2 138 56 130 - 135 SYMBOL Zr Ba Cs I 55 53 PROTONS 40 56 55 53 ELECTRONS 40 54 54 54 NEUTRONS 51 82 80 77 +2 NET CHARGE 0 +1 -1

  14. Calculating AverageAtomic Mass = 79.73 amu 1. Element X has 2 isotopes. The isotope with a mass of 78.92 amu has a relative abundance of 59.35% and 40.65% have a mass of 80.92 amu. Calculate the average atomic mass of X. = (78.92 amu)(0.5935) + (80.92 amu)(.4065)

  15. Calculating AverageAtomic Mass = 24.32 amu 2. Naturally occurring element Z has 3 isotopes. 78.99% have a mass of 24 amu, 10.00% have a mass of 25 amu and 11.01% have a mass of 26 amu. What is the average atomic mass of Z? = (24 amu)(.7899) + (25 amu)(0.10) + (26 amu)(.1101)

  16. Nuclear Chemistry

  17. Nuclear Chemistry • Energy is stored in the nucleus of the atom. • A nuclear reaction is a change that involves the protons and neutrons in an atom. A new element is formed. These reactions gives off energy.

  18. Nuclear Chemistry • Becquerel accidently discovered that uranium emits invisible rays.

  19. Nuclear Chemistry • Marie and Pierre Curie named the process by which uranium gives off rays radioactivity. They isolated many radioactive elements. • This contradicted Dalton’s theory of the indivisible atom. • Elements above #82 (Pb) are naturally radioactive.

  20. Marie Curie & Radioactivity • https://www.youtube.com/watch?v=w6JFRi0Qm_s • https://www.youtube.com/watch?v=TJgc28csgV0

  21. Nuclear Chemistry • Three types of radiation that are given off by nuclear reactions are alpha, beta, and gamma.

  22. High energy radiation He nucleus Electron 0 0 4 2 0 -1 γ He e- +2 -1 0 4 0 0 low moderate very high Very thick lead or concrete Paper, clothing Metal foil

  23. Nuclear Reactions Alpha Emission 238 92 4 2 234 90 U He + Th 226 88 4 2 222 86 Ra + Rn He

  24. Nuclear Reactions Beta Emission 27 12 27 13 0 -1 e Mg + Al 35 17 35 16 0 -1 e + S Cl

  25. Nuclear Reactions Gamma Emission 230 90 226 88 4 2 0 0 + + Th Ra He γ

  26. Half Life • Time it takes for ½ of a radioactive sample to decay. • Ex. C-14 has a half life of 5730 years. F-21 has a half life of 5 sec.

  27. Half Life 1. F-21 has a half life of 5 sec. What fraction of the original nuclei would remind after 20 sec? Half life: (1/2)nn = # cycles n = 20/5 = 4 cycles = (1/2)4 = 0.0625 = 1/16

  28. Half Life B. After 1 minute? (60 s) Half life: (1/2)nn = # cycles n = 60/5 = 12 cycles = (1/2)12 = 2.44 x 10-4 = 1/4096

  29. Half Life C. If the original sample of F-21 had a mass of 250mg, how much would remain after 30 sec? Half life: (1/2)nn = # cycles n = 30/5 = 6 cycles = (1/2)6 = 0.0156 = (0.0156)(250 mg) = 3.91 mg

  30. Nuclear Reactions Fission: a nuclear reaction in which a nucleus is broken into smaller nuclei. Nuclear power plants use controlled fission. 1 0 94 36 1 0 139 56 235 92 n + 3 + Ba Kr + n U

  31. Nuclear Reactions Fusion: a nuclear reaction in which small nuclei join to form larger nuclei. Occurs in the sun and stars. 1 0 2 1 4 2 3 1 + n He + H H

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