The Periodic Law

Electron Configuration and the Periodic Table

The alkaline earth metals

Mg + 2 H2O Mg(OH)2 + H2

Ca + 2 H2O Ca(OH)2 + H2

Be

Ca

Sr

Ba

Ra

Mg

The Alkali MetalsSodium and Water – YouTube

Na + H2O NaOH + H2

Potassium and Water – YouTube

K + H2O KOH + H2

Li

Na

Cs

Fr

K

Rb

Periods and Blocks of the Periodic Table

Write the electron configuration for:

Mg

Ca

F

Cl

1s22s22p63s2

1s22s22p63s23p64s2

1s22s22p5

1s22s22p63s23p5

Sample Problems1. 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 HeliumHydrogen 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 elementsDeviations 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 elementsOxidation 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 elementsMetalloids (semi-metals)• B, Si, Ge, As, Sb, Te, Po?, At?• Properties of both metals and nonmetals

• Brittle solids• Conduct electricity

Silicon

p-Block ElementsMetals• 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 ElementsHalogens• Group 17 nonmetals• Very reactive; react with most metals to

form salts• one electron short of noble gas

configuration• Form -1 ions

F

Cl

Br

I

At

Uuo