The Lanthanides of the Expanded Periodic Table


The lanthanides are a series of chemicals in the expanded periodic table that have an expanded number of orbitals beyond that of the transition metals. The lanthanides are mostly soft metals with their hardness increasing across the period. Whilst they are metals and can conduct electricity the lanthanides have a relatively high resistivity.

Much like the alkali metals the lanthanides are silvery and soft and can be cut with a knife. When exposed to oxygen they will react rapidly to form an oxide layer and tarnish quickly. The lanthanides chemically are all very similar. They will react rapidly with hot water and cold water to produce hydrogen gas. All lanthanides react with elements to form compounds usually with a +3 oxidation state, the most stable for the lanthanides.

Across the lanthanide series there is a decrease in the atomic radius of the atoms as they increase in atomic number due to the increased number of protons in the nucleus. The higher the atomic number the smaller the radius. This decrease is known as the lanthanide contraction.

Terms in section

Resistivity is the ability of a substance to prevent the flow of electrical current and charge, the structure will usually have fewer electrons and large atoms causing collisions when an electrical current is applied

Alkali metals

Alkali metals are located in group 1 of the periodic table. Have a single valence electron which is easily lost from the outer shell. Alkali metals react readily with water to form hydroxides and alkaline pH solutions.

Oxidation state

Oxidation state is the term used to describe the loss or gain of electrons of an element to produce a charged ion

Atomic radius

Atomic radius is the distance measured from the nucleus to the outer valence electrons – measured in pm picometres which is 1x10-12 m

Atomic number

Atomic number is the number of protons in the nucleus


The lanthanides are 15 elements with metallic character from atomic number 57 to 71 exhibiting metallic like properties.

Transition metals

Transition metals are the central section of the periodic table containing the majority of the metals. Also have d sub orbitals producing certain chemical properties

Expanded periodic table

The expanded periodic table is the term given to the periodic table that includes the lanthanides and actinide seres and is wider than the traditional periodic table as it takes into account more periods and groups


Tarnish is a term given as a property of elements where the shiney surface easily loses its shine due to the metal reacting with oxygen in oxidation


Metalloids, the Semi Metals in the Periodic Table


The Actinides of the Expanded Periodic Table