Unit 4- The Periodic Table

1. Unit 4- The Periodic Table • Alkali metals • Alkaline-earth metals • Alloy • Atomic radius • Bond radius • Electron shielding • Electronegativity • Family • Group • Halogen • Ionic radius • Ionization energy • Main-group elements • Metal • Metalloid • Noble/inert gas • Nonmetal • Period • Periodic law • Transition metal • Valence electron

2. The elements of Earth’s crust

3. Cross Classification Grouping by Several Characteristics at Once

4. A Small Problem What is the fastest way to find out which card is missing? • You have 51 cards in a deck. • Grouping the cards by suit and by number reveals the missing card. NUMBERS SUITS

5. The Value of Classification • Classification – grouping based on similarities (just like we did with the playing cards) • Consider a supermarket: • All the dairy foods are in one section. • All the produce is in anothersection. • Grouping helps the shoppers tofind what they are looking for.

6. Refining Classification • Lets take a closer look at the dairy section. • There are additional classifications withinthe dairy section. • Soy products can be in the produce section too! Soy fits in two classifications at once!! Lactaid Soy milk Skim milk Whole milk

7. Cross Classification • Cross Classification - classifying into more than one group at a time • Examples • Deck of cards • Suits and Numbers • Periodic Table • Groups or Families and Periods

8. Cross Classification on the Periodic Table • What do the elements in a vertical column of the Periodic Table have in common? They have the same number of valence electrons.

9. Cross Classification on the Periodic Table • What do the elements in a horizontal row of the Periodic Table have in common? They have the same number of shells.

10. Summary Classification on the Periodic Table • Vertical columns • Called groups or families. • Have elements with similar arrangements of valence electrons. • Valence electron- electrons in the outermost shell of an atom; determines atom’s chemical properties • Horizontal rows • Called periods. • Have elements with the same number of shells.

11. Development of thePeriodic Table Mendeleev Vs Moseley

12. Mendeleev • Dmitri Mendeleev (1869) prepared a card for each of the known elements. He listed • the symbol, • the atomic mass, • and the chemical properties.

13. More Mendeleev • Mendeleev arranged the cards in order of increasing atomic mass. • He noticed a pattern. • The properties repeated regularly.

14. Even More Mendeleev • Mendeleev moved the cards, keeping them in order of mass, so the first one with repeating properties was under the one similar to it. • The cards thus arranged formed groups or families with similar properties. • This arrangement forms the basis for the first Periodic Table.

15. Mendeleev’s Periodic Law • Based on his observations, Mendeleev concluded: • This is known as the Periodic Law. When the elements are arranged in increasing order of atomic mass, the chemical properties repeat periodically.

16. Could Mendeleev be Wrong? No • Look through the Periodic Table. Are all the elements in order with respect to mass? • Which elements are out of order with respect to mass? • Mendeleev was aware of some of these discrepancies. • He knew that if tellurium and iodine werein the right family, they were out of order with respect to mass. • He believed that when scientists improved techniques for measuring atomic mass, these discrepancies would disappear. Ar–K; Co–Ni; Te–I; Th–Pa; U–Np; Pu–Am He was wrong!!

17. Did Mendeleev Make Sense? • Mendeleev found an important pattern − repetition of properties. But does it make sense to think that the pattern is caused by mass? • What parts of an atom affect its mass? • What parts of an atom affect its properties? • Today we know that different isotopes of the same element have the same properties, but have different masses because of neutrons which affect the mass, but not the properties. • Mendeleev does not make sense. Mass does not cause chemical properties. protons and neutrons protons and electrons

18. Moseley • When the elements were ordered so each was in the correct family some were out of order with respect to mass. • When the elements are placed in the proper order, they are numbered sequentially. This number is called the atomic number. • By using a technique called X-ray diffraction, Henry Moseley (1913) showed that the atomic number was the nuclear charge or the number of protons.

19. The Real Periodic Law • Moseley showed that when the elements are arranged in order of atomic number (as measured by X-ray diffraction), the discrepancies in Mendeleev’s Periodic Table disappear. • Moseley corrected the Periodic Law: • This is the basis for the modern Periodic Table. When the elements are arranged in increasing order of atomic number, the chemical properties repeat periodically.

20. How did Mendeleev Succeed (even though he was wrong)? • When Mendeleevarranged the elementsin order of increasingmass, he inadvertentlyarranged them in orderof atomic number, withfew exceptions. • The graph to the rightshows that there is adirect relationshipbetween atomic massand atomic number.

21. What Information is on the Periodic Table? • Each element has its own box on the Periodic Table with a lot of information in it. • There is a key to tell you what information in each box means.Although Periodic Tables differ, most have the same basic information. • Starting from the top of the box, the information on the key to theright is as follows: • [1] atomic mass - weighted average of the mass of the common isotopes of the element; • [2] common oxidation states - tells number of electrons lost, gained or shared during bonding; • [3] symbol - one, two, or three letters related to the name with the first letter capitalized and other letters lower case. The three letter symbols are systematic names that represent the atomic numbers of unnamed elements; • [4] atomic number - number of protons; and • [5] electron configuration - arrangement of electrons in energy levels WRITE DOWN

22. A Quick Tour of The Periodic Table

23. Why is the Periodic Table important to me? • The periodic table is the most useful tool to a chemist. • You get to use it on every test. • It organizes lots of information about all the known elements.

24. Groups…Here’s Where the Periodic Table Gets Useful!! • Elements in the same group have similar chemical and physical properties!! • (Mendeleev did that on purpose.) • Why?? • They have the same number of valence electrons. • They will form the same kinds of ions.

25. Families on the Periodic Table • Columns are also grouped into families. • Families may be one column, or several columns put together. • Families have names rather than numbers. (Just like your family has a common last name.)

26. Hydrogen- it’s own group • Hydrogen belongs to a family of its own. • Hydrogen is a diatomic, reactive gas. • Hydrogen was involved in the explosion of the Hindenberg. • Hydrogen is promising as an alternative fuel source for automobiles

27. Group 1- Alkali Metals • 1st column on the periodic table NOT including hydrogen • Very reactive metals, always combined with something else in nature (like in salt). • Soft enough to cut with a butter knife

28. Group 2- Alkaline Earth Metals • Second column on the periodic table • Reactive metals that are always combined in nature • Several of these elements are important mineral nutrients (such as Mg and Ca

29. Transition Metals • Elements in groups 3-12 • Less reactive harder metals • Includes metals used in jewelry and construction. • Metals used “as metal.” • Used to color paints

30. Group 13- Boron Family • 3 valence electrons • Aluminum metal was once rare and expensive, not a “disposable metal” • B is a metalloid all the rest are metals

31. Group 14- Carbon Family • 4 valence electrons • Nonmetals, metalloids and metals • Contains elements important to life and computers. • Silicon and Germanium are important semiconductors

32. Group 15- Nitrogen Family • 5 valence electrons, tend to share when they are bonded • Nonmetals, metalloids and metals • Nitrogen makes up over ¾ of the atmosphere. • Nitrogen and phosphorus are both important in living things. • Most of the world’s nitrogen is not available to living things. • The red stuff on the tip of matches is phosphorus.

33. Group 16- Oxygen Family • 6 valence electrons • Oxygen is necessary for respiration, most abundant element of Earth’s crust, reactive and combines with many other elements • Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.)

34. Group 17- Halogens • 7 valence electrons • Very reactive, volatile, diatomic, nonmetals • Always found combined with other element in nature • Used as disinfectants and to strengthen teeth.

35. Group 18- The Noble Gases

36. The Noble Gases • Have a full valence shell so… • VERY unreactive, monatomic gases • Used in lighted “neon” signs • Used in blimps to fix the Hindenberg problem.

37. Periodic Table: Metallic arrangement • Layout of the Periodic Table: Metals vs. nonmetals Nonmetals Metals

38. Periodic Table: The three broad ClassesMain, Transition, Rare Earth • Main (Representative), Transition metals, lanthanides and actinides (rare earth)

39. Reading the Periodic Table: Classification • Nonmetals, Metals, Metalloids, Noble gases

40. Properties of Metals • Conduct electricity and heat • Lose valence electrons easily • Malleable- can be pounded into thin sheet • Ductile- can be pulled into wire • Low electronegativity • Solid at room temp. (except Hg) • Different metals can be mixed to form an alloy

41. Properties of Nonmetals • Poor conductor of heat and electricity • Brittle- if solid • Gain or share valence electrons easily • Nonductile • Solid, liquid or gas at room temp. • High electronegativity Sulfur

42. Properties of Metalloids or semi-metals • Solids that can be dull or shiny • Have characteristics of both metals and nonmetals • Ductile and malleable • Conduct heat and electricity better than nonmetals but not as good as metals • Useful in computer chip material

43. Resulting Arrangement • 2 • 3 4 5 6 7 8 9 10 • 12 13 14 15 16 17 18 • 19 20 N O B L E G A S E S M E T A L S • 2 • 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 • 2-8-1 2-8-2 2-8-3 2-8-4 2-8-5 2-8-6 2-8-7 2-8-8 • 2-8-8-1 2-8-8-2 B C Si Ge As Sb Te N O N M E T A L S

44. Trends in the Periodic Table Interpreting the Periodic Table

45. Going across the table from left to right within a row or period • The number of protons increases. • The pull on the electrons increases. • Metallic properties decrease (except in the transition elements) • Ionization energy increases. • Ionization energy - energy needed to remove the most loosely held electron from an element in the gaseous phase • Found in Table S • Electronegativity increases (also Table S). • There is a gradual change from positive oxidation states to negative oxidation states. • The number of valence electrons increases. • The number of shells remains the same.

46. Going down the table within a group or family • The number of protons increases. • The number of shells increases. • The atomic radius increases. • Gets smaller across table due to more pull from electrons on an increasingly positive nucleus • The pull on the electrons decreases. • Metallic properties increase. • The number of valence electrons remains the same.

47. Trend in Atomic Radius • Atomic Radius: • The size of at atomic specie as determine by the boundaries of the valence e-. Largest atomic species are those found in the SW corner since these atoms have the largest n, but the smallest Zeff. • Ionic Radius: • -radius of ions • Follows the same trends as atomic radius

48. Trend in Electronegativity Electronegativity: Discovered by Linus Pauling - A scale of numerical values that reflect how much an atom in a molecule attracts electrons

49. Trend in Ionization Energy Ionization potential: The energy required to remove the valence electron from an atomic specie. Largest toward NE corner of PT since these atoms hold on to their valence e- the tightest.

50. Trend in Electron Affinity Electron Affinity: The energy change that occurs when a neutral atom gains an electron. Most favorable toward NE corner of PT since these atoms have a great affinity for e-.