Ch. 6 - The Periodic Table &
Periodic Law
I. Development
of the Modern
Periodic Table
(p. 174 - 181)
I
II
III
A. Mendeleev
Dmitri Mendeleev (1869, Russian)
Organized elements
by increasing
atomic mass
Elements with
similar properties
were grouped
together
There were some
discrepancies
A. Mendeleev
Deduced elements existed, but were
undiscovered elements, their properties
could be predicted
B. Moseley
Henry Moseley (1913, British)
Organized elements by increasing
atomic number
Resolved discrepancies in Mendeleev’s
arrangement
This is the way the periodic table is
arranged today!
C. Modern Periodic Table
1
2
3
4
5
6
7
Group (Family)
Period
1. Groups/Families
Vertical columns of periodic table
Each group contains elements with similar
chemical & physical properties (same amount of
valence electrons in each column)
2 numbering systems exist:
Groups # I through VIII with ea. # followed by A or B
• A groups are Main Group Elements (s&p electrons)
• B groups are Transition Elements (d electrons)
Numbered 1 to 18 from left to right
2. Periods
Horizontal rows of periodic table
Periods are numbered top to bottom from
1 to 7
Elements in same period have similarities
in energy levels, but not properties
3. Blocks
Main Group Elements
Transition Metals
Inner Transition
Metals
3. Blocks
1
2
3
4
5
6
7
Overall Configuration
Lanthanides - part of period 6
Actinides - part of period 7
Ch. 6 - The Periodic Table
II. Classification of the
Elements
(pages 182-186)
I
II
III
A. Metallic Character
1
2
3
4
5
6
7
Metals
Nonmetals
Metalloids
1. Metals
Good conductors of heat and electricity
Found in Groups 1 & 2, middle of table in
3-12 and some on right side of table
Have luster, are ductile and malleable
Metallic properties increase as you go
from left to right across a period
a. Alkali Metals
Group 1(IA)
1 Valence electron
Very reactive, form metal oxides
(ex: Li2O)
Electron configuration
ns1
Lowest melting points
Form 1+ ion: Cations
Examples: Li, Na, K
b. Alkaline Earth Metals
Group 2 (IIA)
2 valence electrons
Reactive (not as reactive as alkali metals)
form metal oxides (ex: MgO)
Electron Configuration
ns2
Form 2+ ions
Cations
Examples: Be, Mg, Ca, etc
c. Transition Metals
Groups 3 – 12 (IB – VIIIB)
Reactive (not as reactive as Groups 1 or 2),
can be free elements
Highest melting points
Electron Configuration
ns2(n-1)dx where x is column in d-block
Form variable valence state ions
Always form Cations
Examples: Co, Fe, Pt, etc
3. Metalloids
Sometimes called semiconductors
Form the “stairstep” between metals and
nonmetals
Have properties of both metals and
nonmetals
Examples: B, Si, Sb, Te, As, Ge, Po, At
2. Nonmetals
Not good conductors
Usually brittle solids or gases (1 liquid Br)
Found on right side of periodic table –
AND hydrogen
Hydrogen is it’s own group, reacts rapidly
with oxygen & other elements (has 1
valence electron)
Nonmetal Groups/Families
Boron Group: IIIA typically 3 valence
electrons, also mix of metalloids and metals
Carbon Group: IVA typically 4 valence
electrons, also has metal and metalloids
Nitrogen Group: VA typically 5 valence
electrons, also has metals & metalloids
Oxygen Group: VIA typically 6 valence
electrons, also contains metalloids
a. Halogens
Group 17 (VIIA)
Very reactive
Electron configuration
ns2np5
Form 1- ions – 1 electron short
of noble gas configuration
Typically form salts (NaCl)
Anions
Examples: F, Cl, Br, etc
b. Noble Gases
Group 18 (VIIIA)
Unreactive, inert, “noble”, stable
Electron configuration
ns2np6 full energy level
Have an octet or 8 valence e-
Have a 0 charge, no ions
Helium is stable with 1s2, a duet
Examples: He, Ne, Ar, Kr, etc
B. Chemical Reactivity
Metals
Period - reactivity decreases as you go from left to
right across a period.
Group - reactivity increases as you go down a group
Non-metals
Period - reactivity increases as you go from the left
to the right across a period.
Group - reactivity decreases as you go down the
group.
C. Valence Electrons
Valence Electrons
e- in the outermost s & p energy levels
Stable octet: filled s & p orbitals (8e-) in one
energy level
1A
1
2
3
4
5
6
7
8A
2A
3A 4A 5A 6A 7A
C. Valence Electrons
You can use the Periodic Table to determine
the number of valence electrons
Each group has the same number of valence
electrons
Group #A = # of valence e- (except He)
1A
1
2
3
4
5
8A
2A
3A 4A 5A 6A 7A
D. Lewis Diagrams
Also called electron dot diagrams
Dots represent the valence eEx: Sodium
Ex: Chlorine
Lewis Diagram
for Oxygen