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X Unit 11: The Periodic Table

X Unit 11: The Periodic Table. History of the Periodic Table. Antoine Lavoisier (1743 – 1794) Published Elements of Chemistry in 1789 Included a list of “simple substances” (which we now know to be elements) Formed the basis for the modern list of elements

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X Unit 11: The Periodic Table

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  1. X Unit 11:The Periodic Table

  2. History of the Periodic Table Antoine Lavoisier (1743 – 1794) • Published Elements of Chemistry in 1789 • Included a list of “simple substances” (which we now know to be elements) • Formed the basis for the modern list of elements • Only classified substances as metals or nonmetals

  3. History of the Periodic Table Johann Döbereiner (1780 – 1849) • Classified elements into “triads” • Groups of three elements with related properties and weights • Began in 1817 when he realized Sr was halfway between the weights of Ca and Ba and they all possessed similar traits • Döbereiner’s triads: • Cl, Br, I  S, Se, Te • Ca, Sr, Ba  Li, Na, K

  4. History of the Periodic Table John Newlands (1837 – 1898) • Law of Octaves (1863) • Stated that elements repeated their chemical properties every eighth element • Similar to the idea of octaves in music

  5. History of the Periodic Table Dmitri Mendeleev (1834 – 1907) • Russian chemist (“The father of the P.T.”) • Arranged elements based on accepted atomic masses and properties that he observed • Listed elements with similar characteristics in the same family/group • Left blank spots for predicted elements which would be discovered later

  6. Dmitri Mendeleev (1834 – 1907)

  7. Dmitri Mendeleev (1834 – 1907)

  8. History of the Periodic Table Henry Moseley (1887 – 1915) • English physicist • Arranged elements based on increasing atomic number • Remember: atomic number = # of p+ in nucleus • Periodic table looked similar to Mendeleev’s design since as atomic number increases, so does the atomic mass

  9. Periodic Law • Periodic – occurring at regular intervals • Relates to trends on the periodic table of elements • Modern Periodic Law • When elements are arranged in order of increasing atomic number, there is a periodic repetition of their properties

  10. Reading the Periodic Table • Periods • “Horizontal Rows” on the periodic table • Groups (or Families) • “Vertical Columns” on the periodic table

  11. Reading the Periodic Table • Metalloids – elements having properties of both metals and nonmetals

  12. Properties of Metals/Non-metals/Metalloids • Metals - shiny, smooth, solid at room temperature, good conductors of heat and electricity, malleable and ductile. • Metalloids (along stair step line) physical and chemical properties of both metals and nonmetals- B, Si, Ge, As, Sb, Te • Nonmetals – low melting and boiling points, brittle, dull-looking solids, poor conductors of heat and electricity.

  13. Reading the Periodic Table • Valence e- are periodic! • Notice the similarities • Ex.) Write the noble gas configurations for: • F • Cl • Br • I • GROUPS have similar valence electron configurations!

  14. Groups of Elements • Group 1 = Alkali Metals • Located in Group 1 (except Hydrogen) • Extremely reactive • Want to lose 1 e- to become “noble gas-like” • Group 2 = Alkaline Earth Metals • Also very reactive • Both Group 1 & 2 occur naturally as compounds not elements

  15. Group 1: Alkali MetalsLi, Na, K, Rb, Cs Reaction of potassium + H2O https://www.youtube.com/watch?v=oqMN3y8k9So https://www.youtube.com/watch?v=Jy1DC6Euqj4 Cutting sodium metal

  16. Group 2: Alkaline Earth Metals Be, Mg, Ca, Sr, Ba, Ra Magnesium Magnesium oxide https://www.youtube.com/watch?v=qSr39UwpELo

  17. Groups of Elements • Group 17 = Halogens • Very active nonmetals • Want to gain 1 e- to become like a noble gas

  18. Groups of Elements • Group 18 = Noble Gases • Sometimes called “inert gases” since they generally don’t react • Mainly true, but not always (Kr, Xe will react sometimes) • Have a full valence shell (8 e-)

  19. Groups of Elements • Transition Metals • Located in the center of the Periodic Table • 10 elements wide (“d” orbitals) • Semi-reactive, valuable, crucial to many life processes • Lanthanides and Actinides • Located at the bottom of the Periodic Table • 14 elements wide (“f” orbitals) • Some are radioactive, though not all • Lanthanides = Period 6 • Actinides = Period 7

  20. Alkali Metals = Alkaline Earth Metals = Transition metals = Metalloids = Lanthanides = Halogens = Actinides = Noble Gases =

  21. Periodic Properties & Trends • Electronegativity • Ability of an atom to pull e- towards itself • Linus Pauling: developed scale to demonstrate different electronegativity strengths • Increases going up and to the right • Across a period  more protons in nucleus = more positive charge to pull electrons closer • Down a group more electrons to hold onto = element can’t pull e-as closely

  22. Periodic Properties & Trends • Electronegativity • Ability of an atom to pull e- towards itself • Across a period  more protons in nucleus = more positive charge to pull electrons closer • Down a group more electrons to hold onto = element can’t pull e-as closely

  23. Periodic Properties & Trends • Atomic Radius • Distance between the nucleus and the furthest electron in the valence shell • Increases going down and to the left • Down a group more e- = larger radius • Across a period  elements on the right can pull e- closer to the nucleus (more electronegative) = smaller radius • *Remember* • LLLL  Lower, Left, Large, Loose

  24. Periodic Properties & Trends • Atomic Radius • Increases going down and to the left • *Remember* LLLL  Lower, Left, Large, Loose

  25. Memory Device LLLL: Lower Left, Larger Atoms

  26. Periodic Properties & Trends • Ionization Energy • Energy required to remove an e- from the ground state • 1st I.E. = removing 1 e-, easiest • 2nd I.E. = removing 2 e-, more difficult • 3rd I.E. = removing 3 e-, even more difficult • Ex.) B --> B+ + e- I.E. = 801 kJ/mol • Ex.) B+ --> B+2 + e- I.E.2 = 2427 kJ/mol • Ex.) B+2 --> B+3 + e- I.E.3 = 3660 kJ/mol

  27. Periodic Properties & Trends Ionization Energy • Increases going up and to the right • Down a group more e- for the nucleus to keep track of = easier to rip an e- off • Across a period elements on the right can hold electrons closer (more electronegative) = harder to rip an e- off

  28. Periodic Properties & Trends • Metallic Character • How “metal-like” an element is • Metals lose e- • Most Metallic: Cs, Fr • Least: F, O • Increases going down and to the left • Think about where the metals & nonmetals are located on the periodic table to help you remember!

  29. Periodic Properties & Trends • Ionic Radius • Radius of an atom when e- are lost or gained different from atomic radius • Ionic Radius of Cations • Decreases when e- are removed • Ionic Radius of Anions • Increases when e- are added

  30. + + Li , 78 pm 2e and 3 p Sizes of Ions • CATIONS are SMALLER than the atoms from which they are formed. • Size decreases due to increasing he electron/proton attraction. Li,152 pm 3e and 3p

  31. - - F, 71 pm F , 133 pm 9e and 9p 10 e and 9 p Sizes of Ions • ANIONS are LARGER than the atoms from which they are formed. • Size increases due to more electrons in shell.

  32. Overall Periodic Trends

  33. Summary of Periodic Trends

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