Evolution of the Periodic Table: From Lavoisier to Modern Trends

1. Chemistry 1Chapter 6Modern Periodic Table Last Updated January 6, 2020

2. Antoine Lavoisier • Late 1790s • French Scientists • Compiled a list of elements • Only 23 elements known at the time

3. John Newlands • 1864 • English Chemist • Proposed an organization scheme for the elements based on increasing atomic mass noting that properties repeated every eighth element. • Idea did not work for all elements

4. Meyer and Mendeleev • Meyer-German Chemist • Mendeleev-Russian Chemist • Mendeleev published his organization scheme first and is therefore given more credit.

5. Mendeleev Continued • Mendeleev arranged elements according to increasing atomic masses but into columns with similar properties • Was able to predict the properties of yet undiscovered elements

6. Not entirely accurate as new elements were discovered and atomic masses of known elements were more accurately determined.

7. Henry Mosley • 1913 • English Chemist • Arranged elements according to increasing atomic number • Resulted in clear Periodic Patterns

8. Periodic Law • The periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number

9. Review/Discuss • Groups – Columns • Periods – Rows • Main Block Elements (Groups 1A-8A or 1-2,13-18) • Transition Elements (Groups 1B-8B or 3-12) • 1-18 Newer numbering system for groups

10. Review/Discuss Continued • Metals • Non-metals • Metalloids • Transition • Inner Transition • Alkali-metals • Alkaline Earth Metals • Halogens • Noble Gases

12. Classification of the elements • Valence e- and the Periodic Table • See Figure 6-9 page 160

13. Blocks • s • p • d • f • Know the location of each block

14. Periodic Trends • Atomic Radius  in picometers (1 x 10-12 meters) • Generally Decreases from left to right and increases as you move down the periodic table

16. Ion • Charged Particle due to loss gain or sharing of electrons • Loss of electrons = smaller radius • Gain of electrons = larger radius • Compare Trends from Fig 6-11 pg 163 to Fig 6-14 pg. 166 • Lost e- are generally valence e-

17. Ions Continued • Across Periods moving left to right + ions decrease in size • Ions decrease in size • Down Groups Both + and – ions increase radii

19. Ionization Energy- Energy required to remove an e- from a gaseous atom • First ionization energy = 1 e- to remove • Ionization Energy can be thought of as how strongly an atom’s nucleus holds on to its valence e-

20. Atoms with large ionization energy are less likely to form + ions • Low ionization energy indicates an atom loses e- easily likely to form + ions

22. Octet Rule- atoms tend to lose, gain or share e- in order to acquire a full set of eight valence e- • Electronegativity- ability of an atom to attract e- to itself in a chemical bond • Units are arbitrary and are called Paulings, for Linus Pauling

23. Electronegativity decrease as you move down a group and increases as you move left to right • Lowest electronegative = lower left • Highest electronegative = upper right