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) Property
Mendeleev’s Prediction for “eka-silicon” in 1871
Observed Properties of Germanium (discovered in 1886)
Atomic Weight 72
72.59
Density (g/cm3)
5.5
5.35
Melting Point (°C)
High
947
Color
Dark gray
Grayish white
Formula of oxide
XO2
GeO2

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 Metals Li, Na, K, Rb, Cs
Reaction of potassium + H2O
Cutting sodium metal

16. Group 2: Alkaline Earth Metals
Be, Mg, Ca, Sr, Ba, Ra
Magnesium
Magnesium oxide

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 Lanthanides and Actinides
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. LLLL: Lower Left, Larger Atoms
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 e I.E.2 = 2427 kJ/mol
Ex.) B+2 --> B 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. Sizes of Ions Li +
, 78 pm
2e and 3 p
Li,152 pm
3e and 3p
CATIONS are SMALLER than the atoms from which they are formed.
Size decreases due to increasing he electron/proton attraction.

31. Sizes of Ions F -
, 133 pm
10 e and 9 p
F, 71 pm
9e and 9p
ANIONS are LARGER than the atoms from which they are formed.
Size increases due to more electrons in shell.

32. Overall Periodic Trends
Property
Group Trend
Period Trend
Atomic Radius
Increases going down
Increases to the left
Ionization Energy
Increases going up
Increases to the right
Electronegativity
Metallic Character

33. Summary of Periodic Trends