Unit 4: Periodic Law

1. Unit 4: Periodic Law Chief of Springfield Periodic Police Department Clancy Wiggum

2. Castagno Chemistry Challenge IV • Rules: • 1) You are working as a CLASS! • 2) You will have 5minutes! • 3) There are 11 questions so the highest score gets the points. • POINTS • Class:1st – 2pts, 2nd – 1pt, 3rd – 0pts, 4th – 0pts • Questions?

3. Castagno Chemistry Challenge IV • Sections of the periodic table are known by certain names • On the blank table you are provided, match the section name to the area (lettered A, B, C, etc.). • The list is on the next slide. • You will have 5mins • Questions?

4. Castagno Chemistry Challenge IV • Alkaline Earth Metals • Metalloids • Halogens • Rare Earth Metals • Alkali Metals • Noble Gases • Transition Metals • Actinides • “Ungrouped” Metals • “Ungrouped” non-metals • “Disputed”

5. Castagno Chemistry Challenge IV • Answers are on next slide

6. Castagno Chemistry Challenge IV Unit 4 – Periodic Law F H H H H H H A A A A A A B B B B B B E F F F G G G G D D D D E C E D E D K C Answers: A – Alkali Metals E – Metalloids I – Rare Earths B – Alkaline Earth F – Ungrouped NMs J – Actinides C – Transition Metals G – Halogens K – Disputed D – Ungrouped Metals H – Noble Gases Name: I III JJJJ

7. Unit 4 Objectives • Key terms (Periodic Law, groups, families, rows, columns, atomic radii, ionic radii, ionization energy, electron affinity, electron negativity) • How the modern periodic table was developed and arranged. • The properties of vertical columns and horizontal rows on the periodic table. • The trends in atomic radii, ionic radii, charge, metallic character, ionization energy, electron negativity and electron affinity. • Periodic means to show a pattern. • The periodic table can be used as a predicative device. • For a given element, its properties can be determined by its position on the periodic table. • The number of periods on the periodic table is due to the number existing energy levels • The number of groups on the periodic table is due to the way orbitals are filled by electrons. • Elements with similar properties have similar outer energy level electron configurations.

8. Essential Questions • Why is the Periodic Table arranged the way it is? • How can the Periodic Table be used to make predictions of elemental properties? • GUIDING QUESTIONS: • What are the developments that led to the modern periodic table? • How do vertical columns and horizontal rows on the periodic table compare? • What causes Periodic variation of the properties of the elements? • What are the trends in atomic radii, ionic radii, charge, metallic character, ionization energy and electron affinity?

9. Your Take • Why are some element symbols “not filled in?” (P2) • Where is element 113 and others? Why do they have 3 letters? • Why is the f block under the periodic table? • Why is there a gap between s and p? • Why are atomic masses found in brackets after 84? • What is an ionic charge? (P4) • Why is helium “floating?” • Why are some symbols in different colors? • How long do elements last? (P6) • New v Former “designation?” • How long did it take to make? (P7) • Are they adding new elements? Updating? • Undiscovered elements? • How do they study radioactive elements?

10. History I* • The first recorded discovery of an element was by Hennig Brand. • In an attempt to create the Philosopher’s Stone, he distilled human urine and eventually was left with a white substance that glowed – phosphorus. • The first list of non-classical (earth, air, water, fire) elements was by Antoine Lavoisier in 1789. • 33 elements but the list included light and caloric, as well as hydrochloric acid • Caloric is what scientists believed heat was composed of

11. History II* • In 1817, chemist Johann Wolfgang Dobereiner found ‘triads’ or groups of 3 elements with similar properties (behavior) • Cl, Br, I / Ca, Sr, Ba / S, Se, Te / Li, Na, K • John Newlands, working with 56 elements (23 more than Lavoisier) discovered that organizing the elements by weight resulted in a repeating pattern of properties every 8 elements • Law of Octaves

12. History III* • In 1860, more than 60 elements had been discovered. • Different chemists used different values (ie: atomic mass) for the same element. • This means every table is going to be different. • Cannizzaro, later in the year, presented a widely accepted method to determine the atomic mass. • Chemists were finally closing in on the right organization.

13. Mendeleev I • Wrote down every known element and its properties on cards. • He rearranged them according properties such as reactivity and mass looking for patterns.

14. Mendeleev Reenactment • We can easily recreate what Mendeleev did. • So we shall!

15. Mendeleev’s Table

16. Mendeleev II • When arranged according to atomic mass, elements with similar properties appeared at regular intervals. • A repeating pattern is known as periodic.

17. Mendeleev IIA • But does this actually work? • Take a look at the periodic table. • Are the elements currently arranged by mass?

18. Atomic Mass • A quick glance at the periodic table shows mass increases most of the time. • But why not all of the time?

19. Atomic Mass II • The mass of an element is determined by a “weighted average” of the isotopes an element has. • The most abundant isotopes skews the average towards its weight. • *Hydrogen – 1 is the most abundant hydrogen isotope which is why the atomic mass of hydrogen is almost exactly 1

20. Atomic Mass Unit* • The mass of the proton, neutron, and electron are so SMALL that using them as-is is unnecessarily complex. • Therefore, the three masses were converted into “atomic mass units” to make calculations easier

21. Atomic Mass Unit II* • Proton mass: 1.672 x 10-27 kg • Proton a.m.u.: 1.007 • Neutron mass: 1.674 x 10-27 kg • Neutron a.m.u.: 1.008 • Electron mass: 9.109 x 10-31 kg • Electron a.m.u.: 0.000548

22. Average Atomic Mass I* • In order to calculate the mass of an element that is seen on the periodic table, we utilize the mass of every isotope in a.m.u. • We also need the relative percent abundance of each isotope.

23. Average Atomic Mass II • There are numerous isotopes of carbon but C-12 and C-13 are the most abundant.

24. Average Atomic Mass III • This means our weighted average calculation can ignore C-11 and C-14. • A normal average of C-12 and C-13 would be • (12.0000 + 13.0033) / 2 • = 12.50165 • According to the periodic table, the mass of carbon is 12.011…

25. Average Atomic Mass IV • Our average calculation must take into account PERCENT abundance. • 12.0000 * 98.9% = 11.868 • 13.0033 * 1.1% = 0.143 • Now we add the answers together • 11.868 + 0.143 = 12.011

26. Average Atomic Mass V • The mass on the periodic table refers to 6.02 x 1023 atoms. • Also known as 1 mole. • So atomic mass = “molar mass” of an element • Quantities other than 1 mole can be solved proportionally. • 2 moles = 2x molar mass • 0.33 moles = 0.33x molar mass

27. Mendeleev III • Published his first table in 1869. • Iodine • Mass is less than tellerium. • Because it behaved like F, Cl, and Br, he placed it with those elements instead. • He predicted the existence of 3 elements in 1871. • By 1886, all 3 (Sc, Ga, and Ge) were discovered with properties similar to those he predicted.

28. A Summary of Mendeleev* • Unknown to Mendeleev, Lothar Meyer published his own periodic table. • Despite the obvious lack of the Noble Gases (they had not been discovered yet), Mendeleev’s table is a good predictor of to-be-discovered element’s properties. • Mendeleev initially resisted the placement of Noble Gases into the table. • It was possible to add those elements without disturbing the trends of all the others. • This is why Mendeleev gets the credit – his periodic table was a predictive tool.

29. Nonetheless* • The Iodine-Tellurium problem showed that arranging the elements by mass is not good enough. • Scientists searched for a better way to arrange the elements without having to pick and choose what elements go where. • In other words, there should be characteristic about an atom (element) that takes the choice of placement out of the scientist’s hands.

30. Henry Moseley • Moseley worked with Ernest Rutherford analyzing the nucleus of atoms. • He found the patterns of chemical properties fit better when elements were arranged by the number of protons in the nucleus.

31. Periodic Law • Moseley’s work confirmed that tellerium (an atom with 52 protons) should be placed before iodine (53 protons). • Mendeleev’s principle of periodicity was rewritten into what is now known as periodic law • “The physical and chemical properties of the elements are periodic functions of their atomic numbers.”

32. The Modern Table • In the nearly 150 years since Mendeleev, chemists have discovered (or created) over 50 new elements. • These new elements were inserted into the periodic table based off of the atomic number(number of protons in the nucleus). • As Mendeleev predicted, the new elements fit neatly according to Periodic Law.

33. The Noble Gases • The Noble Gases were a significant find. • Helium was discovered first (1868), but not found on earth until 1895. • Argon was found by Lord Rayleigh and Sir William Ramsay in 1894. • To fit this new class of elements onto the periodic table, Ramsay proposed a new group. • Ramsay also discovered Krypton and Xenon, though did not discover Radon.

34. The Lanthanides and Actinides • Lanthanides • The top row of the “f” block. • The elements are very similar in physical and chemical properties they were difficult to separate and identify. • Actinides • The bottom row of the “f” block. • Composed of all radioactive elements, most of which are manmade. • The reason they are “cut and pasted” below the other elements is to save space.

35. Periods and Blocks

36. Hydrogen and Helium • Hydrogen does not fit with any specific group. • It is placed over Group 1 because it has 1 outer electron. • It does not fit in terms of reactivity or other properties. • Helium • All Noble Gases have 8 outer electrons, Helium has 2. • It is placed over Group 18 (8) because of it’s chemical stability.

37. The s – Block • Consists of two groups • All are metals • Group 1 – Alkali Metals • Most reactive metals known • Not found isolated in nature • Can be cut with a kitchen knife • Group 2 – Alkaline-Earth Metals • Less reactive than alkali’s • Harder, denser, and stronger than alkali’s • Also not found isolated in nature

38. The d – Block • This is the largest block, right in the middle of the table. • Transition Metals • Typical metallic properties • Good conductors of heat • Good conductors of electricity • Typically less reactive than alkali and alkaline-earth metals • Some are extremely nonreactive (Pd, Pt, Au)

39. The p – Block

40. The p – Block II • No specific group names for B, C, N, and O groups. • Halogens (Group 17 (7)) • Most reactive nonmetals • Form compounds known as salts. • Noble Gases (Group 18 (8)) • Least reactive elements • All have full outer shells of electrons • Metalloids • Not a group, but these are elements with intermediate conductive properties.

41. The f – Block • Lanthanides (Top row) • Shiny metals • Similar reactivity to alkaline-earth metals • Actinides (Bottom row) • All radioactive • Th, Pa, U, and Np have all been found naturally on earth.

42. Synthetic Elements* • Every element up to Californium exists naturally on earth. • Tc, Pm, Np, Pu, Am, Cm, Bk, and Cf are produced in significant quantities by laboratories but natural nuclear reactions produce these elements in minute quantities in earth’s crust. • Every element from Einsteinium and on are purely synthetic.

43. Where am I? Challenge #2 • There will be clues on the following slides and you must pick what area of the periodic table they are found in. • The areas are located on pieces of paper throughout the classroom so just stand by your location.

44. Where am I? Locations • Alkali Metals • Alkaline Earth Metals • Transition Metals • “Other” (nongrouped) Metals • Lanthanides • Actinides • Nonmetals (nongrouped) • Halogens • Noble Gases • Metalloids • While there is a guarantee everything WILL BE USED ONCE, there is no guarantee on the maximum.

45. Where am I #1? • I am a metal often used in magnets. • Despite the fact I’m not rare at all I am considered to be “rare earth.”

46. Where am I #2?

47. Where am I #3? • The first element discovered that has an organic origin. • In other words, I was discovered in human urine.

48. Where am I #4?

49. Where am I #5? • My reactions with water are legendary. • I contain elements necessary for batteries and life. • Extremely soft for being solid and float on water.

50. Where am I #6?