1. Chapter 5 The 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 Elements Groups 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 Elements Groups 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 Elements Lanthanides 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
Atomic Radius K Na Li Ar Ne

26. D. Atomic Radius
Atomic Radius
Increases to the LEFT and DOWN

27. D. Atomic Radius Why larger going down? Why smaller to the right?
Higher energy levels have larger orbitals
Shielding - core e- block the attraction between the nucleus and the valence e-
Why smaller to the right?
Increased nuclear charge without additional shielding pulls e- in tighter

29. E. Ionization Energy
First Ionization Energy He Ne Ar Li Na K

30. E. Ionization Energy First Ionization Energy
Increases UP and to the RIGHT

31. E. Ionization Energy Why opposite of atomic radius?
In small atoms, e- are close to the nucleus where the attraction is stronger

32. E. Ionization Energy Successive Ionization Energies 2nd I.E. 1,445 kJ
Large jump in I.E. occurs when a CORE e- is removed.
Mg 1st I.E kJ
2nd I.E. 1,445 kJ
Core e- 3rd I.E. 7,730 kJ

33. E. Ionization Energy Successive Ionization Energies 2nd I.E. 1,815 kJ
Large jump in I.E. occurs when a CORE e- is removed.
Al 1st I.E kJ
2nd I.E. 1,815 kJ
3rd I.E. 2,740 kJ
Core e- 4th I.E. 11,600 kJ

35. Examples
Which atom has the larger radius?
Be or Ba
Ca or Br Ba Ca

36. Examples
Which atom has the higher 1st I.E.?
N or Bi
Ba or Ne N Ne

37. S or S2- Al or Al3+ S2- Al Examples
Which particle has the larger radius?
S or S2-
Al or Al3+
S2- Al

38. Electron Affinity Neutral atoms can also acquire electrons.
The energy change that occurs when an electron is acquired by a neutral atom is call the atoms electron affinity.

39. Electron affinity Trend EA increases left to right
EA decreases going down

40. Electronegativity
Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound.

41. Electronegativity Tend to increase across each period (left to right)
Tend to decrease going down