Chapter 5 The Periodic Law

1. Chapter 5The Periodic Law • Patterns of the Periodic Table

3. Section 1 • History of the Periodic Table

4. History • Atomic masses standardized in 1860 • Mendeleev organized all known elements according to atomic mass and chemical and physical properties

5. History • Medeleev noticed a trend in physical/chemical properties • Trends were “periodic” which means there is a repeating pattern

6. History • Mendeleev left several empty spaces • Predicted that some elements were not discovered yet. • Scandium, Gallium, and Germanium

7. History • Mendeleev arranged elements by atomic mass • In 1911, Henry Moseley arranged elements by nuclear charge (proton or atomic number)

8. History • Periodic Law: The physical and chemical properties of the elements are periodic functions of their atomic numbers. • patterns repeat according to atomic number

9. Modern Periodic Table • About 40 more elements have been discovered or created since Mendeleev’s time

10. Noble Gases • Discovered in 1894 by Lord Rayleigh and Sir William Ramsay (Argon) • Very difficult to discover since they are not reactive (inert) • Helium was discovered to exist on the Sun in 1865, but thought not to exist on Earth. (discovered in 1895)

11. Noble Gases • Ramsay made a new group for Helium and Argon • 1898 Ramsay discovered Krypton and Xenon • Radon discovered two years later by Dorn

12. S block elements Group 1 and 2 • Highly reactive elements • Usually found bonded to other elements in nature (compounds)

13. Group 1 elements • Known as the alkali metals • All have an ns1 outer electron configuration • Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium, Francium

14. Group 2 elements • Known as the alkaline earth metals • ns2 valence electron configuration • Less reactive than Group 1 elements • Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium

15. Hydrogen and Helium • Exceptions • Hydrogen’s properties do not resemble the alkali metals (behaves like a metal under extremely high pressures) • Helium’s E.C. is 1s2, but it doesn’t act like a Group 2 (acts like noble gas)

16. The d-Block ElementsGroups 3-12 • Known as transition metals • Less reactive than alkali metals/alkaline earth metals • Some exist as free elements in nature • Palladium platinum and gold

17. P-Block ElementsGroups 13-18 • Properties vary greatly • Includes metals, metalloids, and nonmetals • Valence electrons are equal to group number minus 10

18. Halogens • Group 17 elements • Fluorine, Chlorine, Bromine, Iodine, and Astatine • valence configuration is ns2 np5 • Most reactive non metals • React vigorously with metals

19. F-block ElementsLanthanides and Actinides • Shiny metals • Most are radioactive • Elements above atomic number 92 (Uranium) are man made

20. Periodic Trends

21. Periodic Law • When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.

22. Chemical Reactivity • Families • Similar valence e- within a group result in similar chemical properties

23. Chemical Reactivity • Alkali Metals • Alkaline Earth Metals • Transition Metals • Halogens • Noble Gases

25. Atomic Radius K • Atomic Radius Na Li Ar Ne