1. Chapter 5
The Periodic Law

2. Chapter 5: The Periodic Law
5.1 History of the Periodic Table
5.2 Electron Configuration and the Periodic Table
5.3 Electron Configuration and Periodic Properties

3. Chapter 5 Notes The Periodic Law
Periodic Table Scientists
Stanislao Cannizzaro
Dmitri Mendeleev
Henry Moseley
Sir William Ramsay

4. Modern Russian Table

5. Chinese Periodic Table

6. Orbital Filling Table

7. Periodic Table with Group Names

8. Chapter 5
The Periodic Law
5.1 History of the Periodic Table

9. Predecessors to the Modern Periodic Table
Dobereiner’s Triads
J.W. Dobereiner classified some elements into groups of three, which he called triads.
similar chemical properties
physical properties varied in an orderly way according to their atomic masses.

10. Antoine Lavoisier 1750 only 17 elements known
1789 Antoine Lavoisier grouped known elements (4 groups)
Metals
Non-metals
Gases
Earths
Next 80 yrs scientists looked for better way to classify known elements

11. Stanislao Cannizzaro (1826-1910)
Italian chemist
Determined a method for accurately measuring the relative masses of atoms
His method allowed chemists to search for a relationship between atomic mass and other properties of elements

12. Mendeleev’s Periodic Table
1869….Dmitri Mendeleev (Russian teacher and chemist) organized known elements while playing solitaire
Made deck of cards with elements
Listed name, mass and properties
Paid attention to how elements reacted in chemical reactions
Dmitri Mendeleev

13. Mendeleev’s Periodic Table
Dmitri Mendeleev

14. Predecessors to the Modern Periodic Table
Mendeleev’s Periodic Table
Dmitri Mendeleev realized that the chemical and physical properties of the elements repeated in an orderly way when he organized the elements according to increasing atomic mass.
In 1869, Mendeleev published a table of the elements organized by increasing atomic mass.
Mendeleev was a Russian scientist and is often referred to as the “Father” of the Periodic Table.
Periodicity is the tendency to recur at regular intervals.

15. Mendeleev’s Table "The chemical properties of the elements are a periodic function of their atomic weights"

16. He called this element eka-Aluminum.
Later it was renamed Gallium after its discovery in 1875

17. Mendeleev's Periodic Table
Vertical columns in atomic weight order
Horizontal rows have similar chemical properties
Mendeleev made some exceptions to
place elements in rows with similar
properties (tellurium & iodine's places were switched)
Missing Elements: gaps existed in Mendeleev’s table
Mendeleev predicted the properties of the “yet to be discovered” elements
(scandium, germanium and gallium)

18. Problems with Mendeleev’s Table
Why didn't some elements fit in order of increasing atomic mass?
Moseley helped to clarify some of the problems…
Why did elements exhibit periodic behavior?

19. Henry Moseley
English physicist who determined the number of positive charges in the nucleus (protons) by measuring the wavelength of the x-rays given off by certain metals in 1913.
He was killed by a sniper in Turkey in August 1915 during WWI. Many people think that Britain lost a future Nobel Prize winner. This is because Nobel Prizes, the most prestigious awards for scientific achievement are awarded only to living people.

20. Moseley and the Periodic Table
Protons and Atomic Number:
X-ray experiments revealed a way to determine the number of protons in the nucleus of an atom
The periodic table was found to be in atomic number order, not atomic mass order!!!
This explained tellurium-iodine anomaly
***Moseley was killed in battle in 1915, during WWI. He was 28 years old
The Periodic Law
The physical and chemical properties of the elements are periodic functions of their atomic numbers

21. Discovery of the Noble Gases
William Ramsay discovers argon
Ramsay discovers krypton and xenon
Helium discovered as a component of the sun, based on the emission spectrum of sunlight
Ramsay finds helium on Earth
Freidrich Dorn discovers radon
1868
1894
1895
1898
1900
Sir William Ramsay

22. The Lanthanides
Early 1900's the elements from cerium (#58) to lutetium (#71) are separated and identified. Also known as the rare earth elements, less than 0.01% naturally occurring.
The Actinides
Discovery (or synthesis) of thorium, # 90 to lawrencium #103
Both groups pulled out of the table for space reasons.
Periodicity:
Elements with similar properties are found at regular intervals within the "periodic" table

24. Periodic Table with Group Names

25. 5.2 Electron Configuration & The Periodic Table
Chapter 5
The Periodic Law
5.2 Electron Configuration & The Periodic Table

26. Sublevel Blocks on the Periodic Table1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Sublevel Blocks on the Periodic Table

27. The Properties of a Group: the Alkali Metals
Easily lose 1 valence electron
(Reducing agents)
React violently with water
React with halogens to form salts

28. The Properties of a Group: the Alkali Earth Metals
Easily loses 2 valence electron
(Reducing agents)
Harder, denser, stronger than Group 1 metals
Higher melting points
Less reactive than Group 1, but too reactive to be found free in nature

29. 5.3 Electron Configuration & Periodic Properties
Chapter 5
The Periodic Law
5.3 Electron Configuration & Periodic Properties

30. Determination of Atomic Radius:
Half of the distance between nuclei in
covalently bonded diatomic molecule
"covalent atomic radii"
Periodic Trends in Atomic Radius:
Radius decreases across a period
Increased effective nuclear charge due
to decreased shielding
Radius increases down a group
Addition of principal quantum levels

31. Table of Atomic Radii

32. How to Achieve an Octet…
Atoms can form ions by gaining or losing electrons to obtain a stable outer configuration
Cation- Positive ion (+) ion
Anion- Negative ion (-) ion
Ions attract (opposites attract)

33. Predicting Ionization
Metals tend to lose electrons
They form cations.
Ex: Na, 1s22s22p63s1 becomes Na+1,1s22s22p6
Nonmetals tend to gain electrons.
They form anions.
Ex: O, 1s22s22p4 becomes O-2, 1s22s22p6

34. Electron Transfer: Anions
When an atom gains electrons it increases its negative charge so it becomes negatively charged. There are now more electrons than protons.
X + e- = X –
Ex: Nitrogen Atom + 7 protons
- 7 electrons
Nitrogen Ion +7 protons
- 10 electrons
Neutral
-3 charge

35. Electron Transfer: Cations
When an atom loses electrons, it loses negative charges so it becomes more positively charged. There are now more protons than electrons.
X - (e-) = X +
Ex: Potassium Atom protons
- 19 electrons
Potassium Ion +19 protons
-18 electrons
Neutral
+1 charge

36. Ionization Energy - the energy required to remove an electron from an atom
Increases for successive electrons taken from
the same atom
Tends to increase across a period
Electrons in the same quantum level do not shield as effectively as electrons in inner levels
Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove
Tends to decrease down a group
Outer electrons are farther from the nucleus

37. Ionization of Magnesium
Mg kJ  Mg+ + e-
Mg kJ  Mg e-
Mg kJ  Mg e-

38. Table of 1st Ionization Energies

39. Another Way to Look at Ionization Energy

40. Electron Affinity - the energy change associated with the addition of an electron
Affinity tends to increase across a period
Affinity tends to decrease down a group
Electrons farther from the nucleus
experience less nuclear attraction
Some irregularities due to repulsive
forces in the relatively small p orbitals

41. Table of Electron Affinities

42. Ionic Radii Cations Anions Positively charged ions
Smaller than the corresponding
atom
Anions
Negatively charged ions
Larger than the corresponding
atom

43. Summation of Periodic Trends

44. Table of Ion Sizes

46. Electronegativity A measure of the ability of an atom in a chemical
compound to attract electrons
Electronegativities tend to increase across
a period
Electronegativities tend to decrease down a
group or remain the same

47. Periodic Table of Electronegativities