The Periodic Table

1. The Periodic Table

2. 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.

3. Pre-Periodic Table Chemistry … • …was a mess!!! • No organization of elements. • Imagine going to a grocery store with no organization!! • Difficult to find information. • Chemistry didn’t make sense.

4. HOW HIS WORKED… Put elements in rows by increasing atomic weight. Put elements in columns by the way they reacted. SOME PROBLEMS… He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) He broke the pattern of increasing atomic weight to keep similar reacting elements together. Dmitri Mendeleev: Father of the Table

5. The Current Periodic Table • Mendeleev wasn’t too far off. • The horizontal rows are called periods and are labeled from 1 to 7. • The vertical columns are called groups are labeled from 1 to 18. • Now the elements are put in rows by increasing ATOMIC NUMBER!! • There is a periodic repetition of their physical & chemical properties when elements are arranged by their atomic number……this is called The Modern Periodic Law.

6. 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.

7. METALS More that ¾ of the known elements are metals. Metals share similar properties: • Good conductors of heat & electricity • Luster • Malleable & ductile • High densities • High boiling points & melting points • Resists stretching & twisting • Solids at room temperature

8. NONMETALS • No luster • Poor conductors • May be solid, liquid or gas • Low densities • Low melting & boiling points

9. METALLOIDS • Also called semimetals • Have properties of both metals and nonmetals

10. 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.)

11. Hydrogen • 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

12. German airship (called a zeppelin) • 804 feet long • In 1937 it caught fire killing 35 of the 97 people on board. • Travelling from Germany to US; caught fire as it was landing in NJ • LZ 129 Hindenburg was a Germanzeppelin. Together with its sister-ship LZ 130 Graf Zeppelin II it was the largest aircraft ever built.

14. LZ 129Hindenburg was a Germanzeppelin. Together with its sister-ship LZ 130 Graf Zeppelin II it was the largest aircraft ever built.

15. A Zeppelin is a type of dirigible, more specifically a type of rigid airship

16. An airship is a buoyantaircraft that can be steered and propelled through the air. Unlike aerodynamic craft (e.g. airplanes and helicopters) which stay aloft by moving an airfoil through the air in order to produce lift, aerostatic craft such as airships (and balloons) stay aloft primarily by means of a cavity (usually quite large) filled with a gas of lesser density than the surrounding atmosphere.

17. In the early days of airships, the primary lifting gas was hydrogen. Until the 1950s, all airships, except for those in the United States, continued to use hydrogen because it offered greater lift and was cheaper than helium.

20. Alkali Metals • 1st column on the periodic table (Group 1) not including hydrogen. • Low densities & melting points • React with oxygen & moisture in air • Most reactive metals, always combined with something else in nature, they are not found uncombined (like salt) • Soft enough to cut with a butter knife • Will react violently with water & are stored under oil or kerosene

21. Alkaline Earth Metals • Second column on the periodic table. (Group 2) • Reactive metals that are always combined with nonmetals in nature. • Several of these elements are important mineral nutrients (such as Mg and Ca • Harder than alkali metals • Less reactive than alkali metals, not stored under oil or kerosene

22. Transition Metals • Elements in groups 3-12 • Less reactive harder metals • Includes metals used in jewelry and construction. • Metals used “as metal.”

23. Boron Family • Elements in group 13 • Aluminum metal was once rare and expensive, not a “disposable metal.”

24. Carbon Family • Elements in group 14 • Contains elements important to life and computers. • Carbon is the basis for an entire branch of chemistry. • Silicon and Germanium are important semiconductors.

25. Nitrogen Family • Elements in group 15 • 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.

26. Oxygen Family • Elements in group 16 • Oxygen is necessary for respiration. • Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.)

27. Halogens • Elements in group 17 • Very reactive, volatile, diatomic, nonmetals • Always found combined with other element in nature . • Form salts when combined with Groups 1 or 2 metals • Used as disinfectants and to strengthen teeth.

28. The Noble Gases

29. The Noble Gases • Elements in group 18 • VERY unreactive, monatomic gases • Occur in atmosphere in very small amounts • Used in lighted “neon” signs • Used in blimps to fix the Hindenberg problem. • Have a full valence shell.

30. TRENDS IN THE PERIODIC TABLE

31. #1 ATOMIC SIZE The size of an atom is generally given in terms of the atomic radius.

32. GROUP TRENDS: Atomic size generally increases as we move down a group. As we descend, electrons are added to successively higher energy levels.

33. PERIOD TRENDS: Atomic size generally decreasesas we move from left to right across a period. As we move across a period, electrons are added to the same energy level.

34. Protons are also added to the nucleus. The effect of the increasing nuclear charge on the outermost electrons is to pull than closer to the nucleus. Atomic size, therefore decreases.

35. #2 IONIZATION ENERGY The amount of energy required to remove an electron from an atom.

36. When the outermost electron is located close to the nucleus, there is a greater attraction between the positive protons (in the nucleus) and the negative electrons. • Because of this, more energy is required to remove an electron.

37. When the outermost electrons are further from the nucleus, the attractive force is less, and it is easier to remove an electron. Therefore, the smaller the atom, the higher the ionization energy.

38. GROUP TRENDS: Ionization energy decreases as we go down a group PERIOD TRENDS: Ionization energy increases as we go across a period

39. #3 ELECTRON AFFINITY The amount of energy released when an electron is added to an atom.

40. When electrons are added close to the nucleus, there is a greater attraction between the negative electron and the positive nucleus and electron affinity is higher. • Therefore, the smaller the atom, the higher the electron affinity.

41. GROUP TRENDS: • Electron affinity generally decreasesas we go down a group PERIOD TRENDS: Electron affinity generally increases as we go across a period.

42. #4 IONIC SIZE The size of an ion.

43. Metals…… low ionization energy form positive ions easily • Nonmetals…. high ionization energy form negative ions easily

44. CATIONS: are always smaller than the neutral atom • Atom loses outer shell electron • Increased attraction of nucleus on remaining electrons

45. ANIONS: are always larger than the neutral atom • Nuclear attraction is less for the increased number of electrons • Additional electrons also increases the repulsive forces between electrons

46. GROUP TRENDS: • Ionic size generally increases as we go down a group PERIOD TRENDS: Ionic size generally increases for anions And decreases for cations as we go across a period left to right.

47. #5 ELECTRONEGATIVITY Describes an atoms ability to attract electrons. This trend is similar to electron affinity.

48. GROUP TRENDS: • Electronegativity generally decreasesas we go down a group PERIOD TRENDS: Electronegativity generally increasesas we go across a period.

49. EXCEPTIONS………. • Nobel gases are not included in this general trend.

50. CHEMISTRY NEGATIVITY The feeling you have the day after a Chemistry term Test!