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Periodic Law

Periodic Law. Do Now: What does an element’s position on the periodic table indicate about its properties?. Organizing the Elements. Cu, Ag, Au are three of the oldest known elements. By the year 1700, only 13 elements had been identified and isolated.

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Periodic Law

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  1. Periodic Law

  2. Do Now: What does an element’s position on the periodic table indicate about its properties?

  3. Organizing the Elements • Cu, Ag, Au are three of the oldest known elements. • By the year 1700, only 13 elements had been identified and isolated. • From 1765-1775, five new elements including H, N, and O had been isolated. • As soon as elements were (are) identified, scientists begin to look for similarities and classify them.

  4. Classifying Elements • JW Dobereiner published a classification system in 1829. • Elements grouped in triads (3 elements with similar properties) • Couldn’t group all elements using that system • Dmitri Mendeleev published a table of elements in 1869 • Organized in order of increasing atomic mass

  5. periodic tables

  6. Mendeleev’s Table When classifying elements, Mendeleev organized according to atomic mass. He left spaces (look for question marks) where undiscovered elements would most likely fit. As these elements were discovered, their properties nearly matched those he predicted. His table gained widespread acceptance.

  7. Pledge Comic

  8. The Periodic Law • In developing the Periodic Table, Mendeleev noticed problems. • Atomic mass order didn’t always match periodic trends. • The table was eventually rearranged according to atomic number. In the modern periodic table, elements are arranged in order of increasing atomic number.

  9. Rows or Periods • 7 rows (called periods) on the periodic table • Period 1 has 2 elements • Period 2 has 8 elements • Period 4 has 18 elements • Period 6 has 32 elements • Each period corresponds to a principle energy level • Higher periods have more elements because there are more orbitals in higher energy levels

  10. Columns or Groups • Groups have similar properties. • Properties change across a period but those properties repeat as you move from period to period • Periodic Law: when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

  11. The properties of an element are similar to those of other elements in the same group.

  12. Periodic Law: • When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

  13. Horizontal rows = periods •There are 7 periods • Vertical column = group(or family) • •Similar physical & chemical prop. • •Identified by number & letter (IA, IIA…)

  14. Metals, Nonmetals, Metalloids • 3 broad classes of elements • Across a period, elements become less metallic, and more nonmetallic

  15. Metals, Nonmetals, and Metalloids

  16. Basic Properties of Elements

  17. Metals • 80% of the elements are considered to be metallic • Freshly cut metals have high luster

  18. All metals are solid at room temperature-except Hg • Most metals are ductile and malleable (can be drawn into wires and hammered into thin sheets)

  19. Nonmetals • MOST nonmetals are gases at room temperature • Some are solids (carbon, sulfur, etc) • One is a liquid- bromine Poor conductors of electricity Exception-carbon

  20. http://www.boston.com/bigpicture/2009/06/sulfur_mining_in_kawah_ijen.htmlhttp://www.boston.com/bigpicture/2009/06/sulfur_mining_in_kawah_ijen.html

  21. Metalloids • “stair step” line separates metals from nonmetals-the elements along this line are known as metalloids • Have properties similar to metals and nonmetals • Chemists do not always agree on which elements to classify as metalloids

  22. http://www.ehow.com/info_8675759_uses-metalloids-industry.htmlhttp://www.ehow.com/info_8675759_uses-metalloids-industry.html

  23. Do Now • Which of the following is least likely to be a metalloid? • A. As • B. Hg • C. Ge • D. Si • E. Sb

  24. Classifying Elements • Squares in the Periodic Table tell us: • Atomic # • Element name-black/solid, gases/red, blue/liquid • Average atomic mass • Vertical column of numbers in the top right corner-number of electrons in each occupied energy level

  25. B

  26. Do Now • Chemical properties of the elements are defined by the • A. Electrons • B. Ionization energy • C. Protons • D. Neutrons • E. electronegativity

  27. A

  28. Sort Elements based on Electron Configuration • Noble gases- s and p sublevels full ex: Ar 1s22s22p63s23p6 Representative elements- Group 1A-7A group #=# of electrons in highest occupied energy level

  29. Transition Metals • Transition metals-have electrons in the dorbitals • Inner transition metals- have electrons in the f orbital

  30. In a chemical reaction, the outermost electrons make first contact – this is why elements with similar electron structures have similar chemical properties

  31. Ex: all of the elements in group VII have s2p5 in the outermost shell, so they are all going to want to gain an electron to make a stable octet

  32. Questions • What 4 classes can elements be sorted based on their electron configuration?

  33. Representative elements, noble gases, transition metals, inner transition metals

  34. How many electrons are in the highest energy level of a Group 5A element?

  35. 5

  36. Locate the block this element can be found based on its electron configuration: 1s22s22p63s23p64s23d6

  37. 1s22s22p63s23p63d64s2 Transition metal

  38. Classifying the elements even further…..

  39. Family (Group) Names • Group I - Alkalai metals • Group II – Earth metals • Group III – Boron group • Group IV – Carbon group

  40. Group V – Nitrogen group • Group VI – Oxygen group (Chalcogens) • Group VII – Halogens • Group VIII – Noble Gases

  41. Do Now • A solid element has 2 valence electrons. That element must be • A. A halogen • B. A noble gas • C. A radioactive element • D. an alkalai metal • E. An alkaline earth metal

  42. Do Now • Which pair of elements is expected to have the most similar properties? • A. Potassium and lithium • B. Sulfur and phosphorus • C. Silicon and carbon • D. Strontium and barium • E. Fluorine and iodine

  43. Atomic Size • The electron “cloud” does not have an edge, it is a probability…so how can we measure how large these atoms are? • Measure more than one at a time

  44. Atomic radius- • how we measure the size of an atom- • defined as half the distance between 2 nuclei of a diatomic molecule

  45. Nucleus TotalDistance between 2 nuclei Atomic radius

  46. ALL periodic trends • Are influenced by 3 factors: • 1. Energy Level- higher energy levels are farther away from the nucleus • 2. Charge on nucleus (number of protons)- the more charge pulls electrons closer (+ and – attract)

  47. 3. Shielding- electrons in lower energy levels “block” the positive pull of the nucleus from the outer electrons

  48. Periodic Trends 1. ATOMIC RADIUS • Going from left to right across a period the atomic radius (size) getssmaller because: • Electrons are in the same energy level • But there is more nuclear charge • Outermost electrons are pulled closer

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