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Section 1B

Section 1B. Periodic Trends. Unit Challenge – Greener Than Greenbacks ?. Unit Challenge – Checklist. Lifespan dollar bills/coins Economic costs Environmental costs/impacts of producing, disposing and recycling Chemical properties of materials Materials that make up bills/coins

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Section 1B

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  1. Section 1B Periodic Trends

  2. Unit Challenge – Greener Than Greenbacks?

  3. Unit Challenge – Checklist • Lifespan dollar bills/coins • Economic costs • Environmental costs/impactsof producing, disposing and recycling • Chemical properties of materials • Materials that make up bills/coins • Availability of materials/resources

  4. Section 1B Grouping the Elements

  5. Grouping Elements • By the mid-1800s, chemists had identified about 60 elements. Five of these elements were nonmetals that are gases at room temperature: hydrogen (H), oxygen (O), nitrogen (N), fluorine (F), and chlorine (Cl). Two liquid elements were also known, the metal mercury (Hg) and the nonmetal bromine (Br). The rest of the known elements were solids with widely differing properties. To organize information about the known elements, several scientists tried to place elements with similar properties near one another in a chart. Such an arrangement is called a periodic table. Dimitri Mendeleev, a Russian chemist, published a periodic table in 1869 similar to the one we use today. • In some respects, the periodic table has a pattern that resembles a monthly calendar, in which weeks repeat in a regular (periodic) seven-day cycle.

  6. Element Discovery Dates

  7. Grouping Elements Cut out the cards and arrange the cards in order of increasing atomic mass. Try sorting the cards into several different groups. Each group should include elements with similar properties. You might need to try several methods of grouping before you find one that makes sense to your group. Examine the cards within each group for any patterns. Arrange the cards within each group in some logical sequence. Again, trial and error may be a useful method for accomplishing this task. Observe how particular element properties vary from group to group. Arrange all the card groups into some logical sequence. Select the most reasonable and useful patternwithin and among card groups. Then tape the cards onto a blank sheet of paper to preserve your pattern for a later classroom discussion.

  8. Grouping Elements • How and why did you: • group the elements? • arrange the elements within groups? • arrange the groups? Answer these three questions in your notebook with supporting evidence from your cards

  9. Mendeleev’s Periodic Table

  10. Section 1B Atomic Components

  11. Atomic Components • How are atoms electrically neutral? • Contain the same number of positive and negative pieces • Protons (+) • Electrons (-) • Example: Neutral sodium has 11 protons and 11 electrons

  12. Atomic Components • What are neutrons? • Pieces of atom that are neutral (have no charge) • Located in the nucleus with the protons

  13. Atomic Number • What is the significance of the atomic number? • Indicates how many protons there are in the element • ONLY way to identify an element

  14. Atomic Components

  15. Atomic Mass • How do we determine the mass of an atom? • Add the mass of the p, n and e • Use the atomic mass/mass number • Unit: Atomic Mass Unit (AMU) • Proton – 1 AMU • Neutron – 1 AMU • Electron – 0 AMU (because they’re so small)

  16. Atomic Components • How do we figure out how many neutrons are in a nucleus? • Identify the atomic mass • Subtract the protons (atomic number) • Round DOWN the remaining number (can’t have a part of a neutron) Example: Zinc has 35 neutrons. 65.39 – 30 = 35.39 (round down)

  17. Atomic Components • Why don’t we subtract out electrons? • We assume that they have no mass because they are so small • Remember, 0 AMU

  18. Atomic Components • What happens if the number of protons and electrons is not equal? • Atom becomes charged • More protons, + charge • Called a cation • More electrons, - charge • Called an anion • Example: Potassium with 19 protons and 18 electrons has a 1+ charge

  19. Electrons • How do we determine the number of electrons in a charged atom? • Add or subtract the charge to or from the atomic number • Negative charge means you have more electrons  ADD • Positive charge means you have less electrons  SUBTRACT Remember! Electrons are negative so when you subtract them you are subtracting negatives!

  20. Atomic Components

  21. Section 1B Periodic Families and Trends

  22. Periodic Table Organization • What are the horizontal rows on a periodic table called? • Periods • Elements are organized by increasing atomic number

  23. Periodic Table Organization • What are the vertical columns on a periodic table called? • Groups or Families • Elements in the same group have very similar physical and chemical properties

  24. Periodic Table Organization • What are some of the important groups/families? • Group 1 – Alkali metals (not H) • 1:1 ratio with Cl (chloride) • 2:1 ratio with O (oxide) • Group 2 – Alkaline earth metals • Group 17 – Halogens (or Halides) • Group 18 – Noble Gases

  25. Periodic Table Organization • What are periodic trends? • Patterns in properties • Allows scientists to predict the chemical and physical properties of elements

  26. Mendeleev’s Periodic Table

  27. Predicting Properties #1 In your notebook, answer and explain. Given that the density of silicon (Si) is 2.3 g/cm3and the density of tin (Sn) is 7.3 g/cm3, estimate the density of germanium (Ge).

  28. Predicting Properties #2 In your notebook, answer and explain. The element krypton (Kr) was not known in Mendeleev’s time. Given that the boiling point of argon (Ar) is –186 °C and of xenon (Xe) is –107 °C, estimate the boiling point of krypton.

  29. Predicting Properties #3 In your notebook, answer and explain. Mendeleev knew that silicon tetrachloride (SiCl4) existed. Using his periodic table, he correctly predicted the existence of ekasilicon, which we now know as germanium. Predict the formula for the compound formed by germanium and chlorine.

  30. Predicting Properties #4 In your notebook, answer and explain. Elemental nickel is white to light gray in color, highly ductile, lustrous, and resistant to tarnish. Explain which other element you would expect to share these properties: Cu, Rb, Pt or Kr?

  31. Predicting Properties #5 In your notebook, answer and explain. Here are formulas for several known compounds: NaI, MgCl2, CaO, Al2O3, and CCl4 Using that information, predict the formula for a compound formed from: • C and F • Al and S • K and Cl • Ca and Br • Srand O

  32. Predicting Properties #6 In your notebook, answer and explain. Estimate the melting point of rubidium (Rb). The melting points of potassium (K) and cesium (Cs) are 337 K and 302 K, respectively. Do you expect the melting point of sodium (Na) to be higher or lower than that of rubidium (Rb)? Explain. On what evidence did you base your answer?

  33. Predicting Properties #7 In your notebook, answer and explain. Manganese, which has melting point 1519 K and is one of the metals used in the Presidential dollar coin, was the only known element in its family for 150 years. When rhenium, which hasmelting point 3459 K, was discovered in 1925, what could chemists predict about the melting point of element 43 (which was still unknown at the time)?

  34. Halogen Family As you learned earlier, elements were placed in columns on the periodic table because they had similar chemical and physical properties. In this investigation, you will examine some characteristics of elements from one family. Group 17, which consists of the elements fluorine, chlorine, bromine, iodine and astatine, is called the halogengroup. When elements in this group form compounds, those compounds are known as halide compounds. In this investigation, you will determine which halogens and halide compounds react with one another and develop a rule to summarize those interactions.

  35. Halogen Family Table (7x7)

  36. Halogen Family • How do we know a chemical reaction took place? • Color changes • Example: Tube 1 changed from clear to purple

  37. Halogen Family • What is the trend in reactivity within the halogen family? • Cl – most reactive • I – least reactive • Halogens increase in reactivity as you move up the group

  38. Section 1B Ions and Ionic Compounds

  39. Ionic Compounds How do sodium and chlorine combine? Oppositely charged ions attract each other Called an ionic compound Na1+ and Cl1- chemically combine to create sodium chloride (NaCl) crystals

  40. Ionic Compounds How do we make a chemical formula neutral? The total charge of the ions in the molecule EQUALS zero Must have positive and negative ions to do this If the charges don’t automatically cancel out use subscripts to balance them

  41. Ionic Compounds • How do we write formulas for ionic compounds? • Write the cation first and then the anion • Use subscripts to show the fewest number of ions that total zero

  42. Ionic Compounds • What is the formula for magnesium and bromine? • Mg2+ and Br1- • For every 1 Mg2+ you need 2 Br1- • MgBr2 - Br Mg + + - Br

  43. Ionic Compounds • How do you name ionic compounds? • Change the ending (suffix) of the anion to –ide • Example: MgBr2 • Magnesium Bromine • Magnesium Bromide

  44. Ionic Compounds • How do you name a metal that has more than one charge? • With roman numerals to represent the charge • Ex. Iron • Fe2+ is Iron (II) • Fe3+ is Iron (III) • Example: Fe2O3 • Iron (III) Oxide

  45. Ionic Compounds • What are polyatomic ions? • A combination of two or more atoms that have a charge • Treat the polyatomic as one piecewith one charge • Never change its name! • Example: Lithium Nitrate • LiNO3 - NO3 Li +

  46. Ion Puzzle Cards

  47. Ion Puzzle Cards Please combine the following ion puzzle pieces and complete the table on your data worksheet. Barium and Chlorine Potassium and Bromine Cesium and Fluorine Silver and Chlorine Scandium and Nitrogen

  48. Ion Puzzle Cards Continued Barium and Hydroxide Aluminum and Hydroxide Zinc and Chlorine Barium and Sulfur Potassium and Cyanide Ammoniumand Chlorine Lead andChlorine Zincand Carbonate Sodium andOxygen Lead and Sulfur (Careful with this one!)

  49. Ionic CompoundsAdvanced Practice • Sodium iodide was one of the sources of halide ions used in the demonstration. • The blue solution you used in LAB 1A was probably copper (II) chloride. • Baking soda is sodium hydrogen carbonate. • CaSO4is a component of plaster. • A substance composed of Ca2+and PO34-ions is found in some brands of phosphorus-containing fertilizer. • Ammonium nitrate, a rich source of nitrogen, is often used in fertilizer mixtures. • Aluminum sulfate is a compound sometimes used to help purify water. • Magnesium hydroxide is called milk of magnesia when it is mixed with water. • Limestone and marble are two common forms of the compound calcium carbonate. • Silver nitrate, a compound used to make photographic film, will also be used in an upcoming investigation.

  50. Section 1B Metal Activity Series

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