1. PSC Chap. 4
The Periodic Table

2. In modern periodic table, elements in the same column have similar properties.

3. John Newlands - Law of Octaves
arranged first 16 elements in order of atomic mass
found that similar properties were found every 8th element

4. Dmitri Mendeleev - invented the modern periodic system - basis of the modern periodic table
arranged all known elements in order of atomic mass
placed elements w/ similar properties in vertical columns

5. A couple of problems w/ Mendeleev's table
Some elements did not fit into the right columns when put in order of atomic mass. If switched, they fit.
-ex. Te and I, Co and Ni

6. A couple of problems w/ Mendeleev's table
In order to put some elements in the right column, gaps had to be left in his table.
He predicted elements would be discovered to fill the gaps
Also correctly predicted properties of these undiscovered elements

7. Henry Mosely, using X-rays, discovered the atomic number of elements.

8. When elements in Mendeleev's table were placed in order of atomic number, they fell into the right columns.

9. Periodic Law
- the physical and chemical properties of elements are a periodic function of their atomic numbers

10. Period or Series
elements that form a horizontal row in the periodic table
all elements in the same series have the same outer energy level

11. Group or Family
elements that form a vertical column in the periodic table
elements in the same group have similar electron configurations
also have similar properties.

12. Periodic Table can be divided into 2 regions
Metals - left side of table
good conductors of electricity and heat
shiny
malleable
groups 1-12 and some of groups 13-16
Nonmetals - right side of table
poor conductors of electricity and heat
dull
brittle
some of groups and all of groups 17 & 18

13. Metalloids Semiconductors (semi-metals)
Have properties of both metals and nonmetals
lie on dividing line
used to make transistors and computer chips

14. Main-Group Elements Also called representative elements
s and p block elements
have consistent electron configurations

15. Group 1 Alkali Metals all end in s1 lose the outer e- to form +1 ions
Very reactive metals
React w/ water and oxygen
soft

16. Group 2 Alkaline Earth Metals Active metals end in s2
lose 2 outer e-’s to form +2 ions
not as soft as group 1 metals

17. Transition Metals d block elements not as reactive as groups 1 and 2
highest energy e-’s are in the d sublevel
not as reactive as groups 1 and 2
have varied properties

18. Lanthanides and Actinides
f block elements
highest energy e-’s are in the f sublevel
sometimes called rare earth elements or inner-transition elements
Lanthanide series fills 4f sublevel
shiny, reactive, irregular configurations

19. Lanthanides and Actinides
Actinide series fills 5f sublevel
radioactive

20. Group 16
Chalcogens
Contains active nonmetals (top) to metalloids to less active metals
end in s2p4
nonmetals gain 2 e-’s to form -2 ions

21. Group 17 Halogens Most reactive nonmetals
react with metals to form salts
end in s2p5
gain 1 e- to form -1 ions

22. Group 18
Noble Gases
Mostly unreactive
end in s2p6

23. Hydrogen In a class by itself
Behaves unlike other elements because it has only 1 p+ and 1 e-
Most common element in the universe

24. Properties of elements are determined by their electron configurations.
Elements with similar properties have similar electron configurations.

25. Periodic Trends
Atomic radii
Reactivity

26. Atomic radius Atomic radius increases as you move down a group
Add an energy level as you move down
Atomic radius decreases as you move across a period
Increased nuclear charge pulls e- cloud in tighter

27. Reactivity of Metals Metals tend to lose e-’s
As you move down a group, reactivity of metals increases
Atoms are bigger and e-’s are held less tightly
As you move to the left, reactivity of metals increases
atoms are bigger to the left

28. Reactivity of Metals
The most active metal is in the lower left corner of the periodic table. Fr

29. Reactivity of Nonmetals
Nonmetals tend to gain e-’s
As you move up a group, reactivity of nonmetals increases
Atoms are smaller and hold e-’s more tightly
As you move to the right, reactivity of nonmetals increases (noble gases not considered)
Atoms are smaller

30. Reactivity of Nonmetals
The most active nonmetal is in the upper right corner of the periodic table. F

31. First Ionization Energy
The attraction of an atom for e-’s determines the type of bond formed on a comp.
Ionization Energy – energy required to remove an e- from an atom
First Ionization Energy – energy required to remove the most loosely held e- in an atom
(KJ/mole)

32. First Ionization Energy
Ionization energies are periodic properties
Tend to incr as Z incr in a period (left to right)
Tend to decr as you move down a group
Metals have low ioniz energies
Nonmetals have high ioniz energies

33. First Ionization Energy
As you go dn a column, outer level e-’s are farther from the nucleus
\ held less tightly
Also, there’s a decr in nuclear attraction betw outer e-’s & nucleus bec of other e-’s betw them
Shielding Effect
E-’s are held less tightly – less energy to remove them
\ lower ionization energy

34. First Ionization Energy
As you move across the table in a period, atoms get smaller bec of increased nuclear attraction
E-’s held tighter, \ higher ionization energy

35. First Ionization Energy
There are deviations from the expected as we move across the table
Small decr betw Be (1s22s2) & B (1s22s22p1)
Be – a 2s e- must be removed from a fairly stable atom
B – a lone 2p e- must be removed
Ion is more stable, \ takes less energy
Small decr betw N(1s22s22p3) & O (1s22s22p4)
N is more stable w/ ½-filled sublevel

36. Factors Affecting Ionization Energy
Nuclear Charge (nuclear attraction)
Shielding Effect
Radius
Sublevel