1 / 41

Unit 4: Periodicity and Nuclear Chemistry

Unit 4: Periodicity and Nuclear Chemistry. C.5.C use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy C.12.A describe the characteristics of alpha, beta, and gamma radiation

oria
Download Presentation

Unit 4: Periodicity and Nuclear Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit 4: Periodicity and Nuclear Chemistry C.5.C use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy C.12.A describe the characteristics of alpha, beta, and gamma radiation C.12.B describe radioactive decay process in terms of balanced nuclear equations C.12.C compare fission and fusion reactions

  2. Table of Contents • Periodicity 3-17 • Nuclear Chemistry I Types of Radiation and Nuclear formulas 18-29 • Nuclear Chemistry II Nuclear Fission and Fusion & Half-Life 30-41

  3. Periodicity Periodic Trends

  4. Periodic Law • The chemical and physical properties of the elements are periodic functions of their atomic numbers; properties of the elements occurred at repeated intervals called periods. • This defines the property of periodicity

  5. Periodic Trends • properties that show patterns when examined across the periods or vertically down the groups • while there are many periodic trends, we will focus on • atomic radii (the plural of radius) • ionization energy • Electronegativity • Ionic radii (the plural of radius)

  6. Atomic Radii • One half the distance between the nuclei of identical atoms that are bonded together. • Distance between nuclei decreases across periods because the higher nuclear charge (positive) pulls the electrons closer to the nucleus • increases down groups because energy levels are being added outside the nucleus

  7. Atomic Radii Decreases Atomic Radii Increases

  8. Graphing Atomic radii The graph of Atomic Radius vs. Atomic Number shows the trend in atomic radius as one proceeds through the first 37 elements in the periodic table.

  9. Ionization Energy • The energy required to remove one electron from a neutral atom of an element. • increases across periods because it takes more energy to overcome the electrons attraction to the increasing nuclear charge • decreases down groups because it is easier to overcome the nuclear charge for the outermost electrons as the number of energy levels increases

  10. Graphing Ionization Energy • These trends are visible in the graph of ionization energy versus atomic number.

  11. Electronegativity • a measure of the ability of an atom in a compound to attract electrons from other atoms • increases across periods as a result of the increasing nuclear charge and ability of the nucleus to attract electrons from a neighboring atom • decreases down groups because the nuclear charge is less able to attract electrons from another atom as additional energy levels are added

  12. Graphing Electronegativity The graph of Electronegativity vs. Atomic Number shows the trend in the electronegativity as one proceeds through the first 37 elements in the periodic table.

  13. Ionic Radii • The radius of an atom forming ionic bond or an ion. The radius of each atom in an ionic bond will be different than that in a covalent bond. • The reason for the variability in radius is due to the fact that the atoms in an ionic bond are of greatly different size. One of the atoms is a cation, which is smaller in size, and the other atom is an anion which is a lot larger in size.

  14. decreases across the period until formation of the negative ions then there is a sudden increase followed by a steady decrease to the end • The sudden increase on formation of negative ions is due to the new (larger) outer shell

  15. Graphing ionic radii

  16. Nuclear Chemistry I. Types of radiation & Nuclear formulas

  17. Introduction to Nuclear Chemistry Nuclear Chemistry Nuclear Reactions • Nuclear chemistry is the study of the structure of atomic nuclei and the nuclear change they undergo. • Characteristics: • Isotopes of one element are changed into isotopes of another element • Contents of the nucleus change • Large amounts of energy are released

  18. Chemical vs. Nuclear Reactions

  19. Chemical Symbols • A chemical symbol looks like… • To find the number of , subtract the from the mass # 14 C atomic # 6 neutrons mass # atomic #

  20. Types of Radiation • Radioactive Decay – when unstable nuclei lose energy by emitting radiation to attain more stable atomic configurations (spontaneous process) • Alpha – radioactive decay of an atomic nucleus that is accompanied by the emission of an alpha particle( ). • Beta – Radioactive decay in which an electron is emitted ( ). • Gamma – High energy photons that are emitted by radioactive nuclei.

  21. Alpha Decay • Alpha decay – emission of an alpha particle (α), denoted by the symbol , because an α has 2 protons and 2 neutrons, just like the He nucleus. Charge is +2 because of the 2 protons • Alpha decay causes the mass number to decrease by 4 and the atomic number to decrease by 2. • Atomic number determines the element. All nuclear equations are balanced. 4 He 2

  22. Alpha Decay • Example 1: Write the nuclear equation for the radioactive decay of polonium – 210 by alpha emission. Step 4: Determine the other product (ensuring everything is balanced). Step 3: Write the alpha particle. Step 2: Draw the arrow. Step 1: Write the element that you are starting with. Mass # 210 4 206 He Po Pb 84 2 82 Atomic #

  23. Beta decay • Beta decay – emission of a beta particle (β), a fast moving electron, denoted by the symbol e- or . β has insignificant mass (0) and the charge is -1 because it’s an electron. • Beta decay causes no change in mass number and causes the atomic number to increase by 1.

  24. Beta Decay • Example : Write the nuclear equation for the radioactive decay of carbon – 14 by beta emission. Step 4: Determine the other product (ensuring everything is balanced). Step 3: Write the beta particle. Step 2: Draw the arrow. Step 1: Write the element that you are starting with. Mass # e 14 0 14 C N -1 6 7 Atomic #

  25. Gamma decay • Gamma rays – high-energy electromagnetic radiation, denoted by the symbol γ. • γ has no mass (0) and no charge (0). Thus, it causes no change in mass or atomic numbers. • Gamma rays almost always accompany alpha and beta radiation. • However, since there is no effect on mass number or atomic number, they are usually omitted from nuclear equations. • Example: ϒ +

  26. Penetration of Radiation • Alpha and beta are particles emitted from an atom.  Gamma radiation is short-wavelength electromagnetic waves (photons) emitted from atoms. • The figures show the penetration of the different types of radiation.

  27. Review 4 2 0 -1

  28. Nuclear Chemistry II. Nuclear Fission and Fusion & Half Life

  29. Nuclear Fission • Fission - splitting of a nucleus. • - Very heavy nucleus is split into two approximately equal fragments. • -Chain reaction releases several neutrons which split more nuclei. • - If controlled, energy is released slowly (like in nuclear reactors). Reaction control depends on reducing the speed of the neutrons (increases the reaction rate) and absorbing extra neutrons (decreases the reaction rate).

  30. Nuclear Fission • - Examples – atomic bomb, current nuclear power plants • → + + 2 x 102 kJ/mol

  31. Nuclear Fusion • Fusion - combining of a nuclei • Two light nuclei combine to form a single heavier nucleus • - Does not occur under standard conditions (+ repels +) • - Advantages compared to fission • Inexpensive, No radioactive waste • - Disadvantages • requires large amount of energy to start, difficult to control

  32. Nuclear Fusion • Examples – energy output of stars, hydrogen bomb, future nuclear power plants

  33. Half-Life • Half Life is the time required for half of a radioisotope’s nuclei to decay into its products. • For any radioisotope,

  34. Half-Life • For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 29 years. How much will be remaining after x number of years?   • You can use a table:

  35. Half-Life • Or an equation! initial mass mt = m0 x (0.5)n mass remaining # of half-lives

  36. Half-Life • Example 1: If gallium – 68 has a half-life of 68.3 minutes, how much of a 160.0 mg sample is left after 1 half life? ________ 2 half lives? __________ 3 half lives? __________

  37. Half-Life • Example 1: If gallium – 68 has a half-life of 68.3 minutes, how much of a 160.0 mg sample is left after 1 half life? ________ mt = 160.0 mg x (0.5)1 = 80.0 mg 2 half lives? __________ mt = 160.0 mg x (0.5)2 = 40.0 mg 3 half lives? __________ mt = 160.0 mg x (0.5)3 = 20.0 mg

  38. Half Life • Iodine-131 is a radioactive isotope with a half-life of 8 days. How many grams of a 64 g sample of iodine-131 will remain at the end of 8 days? ________ • How many grams of a 64 g sample of iodine-131 will remain at the end of 24 days? ________

  39. Half Life • Iodine-131 is a radioactive isotope with a half-life of 8 days. How many grams of a 64 g sample of iodine-131 will remain at the end of 8 days? ________ • Mt = 64 g x (0.5)1 = 32 g • How many grams of a 64 g sample of iodine-131 will remain at the end of 32 days? ________ • First how many ½ lives have gone by. • 32/8 (the ½ of iodine-131) = 4 • Then plug 4 into formula. • Mt = 64 g x (0.5)4 = 4 g

More Related