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Evolution of the Periodic Table: From Lavoisier to Modern Trends

Explore the historical journey and key contributors shaping the periodic table, from Lavoisier to modern trends like electronegativity and atomic radius. Understand elements, groups, properties, and significant classification methods.

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Evolution of the Periodic Table: From Lavoisier to Modern Trends

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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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