The Periodic Law
Electron
Configuration and
the Periodic Table
The alkaline earth metals
Be
Mg
Mg + 2 H2O  Mg(OH)2 + H2
Ca
Sr
Ba
Ra
Ca + 2 H2O  Ca(OH)2 + H2
The Alkali Metals
Li
Na
Sodium and Water – YouTube
Na + H2O  NaOH + H2
K
Rb
Potassium and Water – YouTube
Cs
K + H2O  KOH + H2
Fr
Periods and Blocks of the Periodic Table
Write the electron configuration for:
Mg
1s22s22p63s2
Ca
1s22s22p63s23p64s2
F
1s22s22p5
Cl
1s22s22p63s23p5
Sample Problems
1. Without looking at the periodic table, give the
group, period, and block in which the element with
the electron configuration [Xe]6s2 is located.
Group 2, sixth period, s-block
2. Without looking at the periodic table, write the
electron configuration for the Group 1 element in
the third period. Is this element likely to be more
active or less active than the element in #1?
1s22s22p63s1; more reactive
Hydrogen and Helium
Hydrogen and helium are the most abundant elements
in the universe. Hydrogen makes up 76 % of the mass
of the universe and helium makes up 23 %.
Hydrogen 1s1
• Despite the same outer configuration as the alkali
metals, H has unique properties unlike any other
group.
Helium
1s2
• Although its configuration is similar to the alkaline
earth metals, it has the properties of a noble gas due
to its filled outer energy level.
d-Block elements
d-Block elements
• d-Block elements are known as transition
metals
• Have common metallic properties
• Conduct heat and electricity
• Less reactive than alkali and alkaline earth
metals
• Some are very unreactive: Au, Pt, Pd, Ag
d-Block elements
Deviations from orbital filling:
Nickel (Ni):
[Ar]4s23d8
Palladium (Pd): [Kr]5s04d10
Platinum (Pt):
[Xe]6s14f145d9
• In each case the sum of s and d electrons is 10
d-Block elements
Oxidation States
• Most transition metals are multivalent
Iron (Fe):
[Ar]4s23d6
Iron II (Fe2+):
[Ar]4s13d5
Iron III (Fe3+): [Ar]4s03d5
p-Block elements
• p-Block and s-block elements together are
known as the main group elements.
• Properties vary considerably
• Includes nonmetals, metalloids, and metals
p-Block elements
Metalloids (semi-metals)
• B, Si, Ge, As, Sb, Te, Po?, At?
• Properties of both metals and nonmetals
• Brittle solids
• Conduct electricity
Silicon
p-Block Elements
Metals
• Al, Ga, In, Tl, Sn, Pb, Bi
• Reactive and found in nature as part of
compounds
• Relatively stable in elemental form
• Softer and less dense than d-block metals. (Pb
is an exception.)
p-Block Elements
F
Cl
Br
I
At
Uuo
Halogens
• Group 17 nonmetals
• Very reactive; react with most metals to
form salts
• one electron short of noble gas
configuration
• Form -1 ions