The Actinides of the Expanded Periodic Table


The Actinides also known as the actinoids are a set of elements in the final period of the periodic table from elements 89 to 103. They are a series of radioactive elements with similar properties.

Actinides are found in small quantities in the earth’s crust as thorium and uranium but the large majority of them are synthetic elements and need to be created in particle accelerators due to their high rate of decay and radioactivity.

All of the actinides are radioactive and have no stable isotopes. Being synthetic elements they are very hard to study due to their low half lives and undergoing rapid decay into more stable isotopes. Actinides are very similar in reactivity, tarnishing in air and spontaneously igniting with air. They are also dense metals and have a variety of allotropes, different structures. Plutonium itself has 6 different allotropes exhibiting a variety of crystal structures. Much like the group 1 metals they will react readily with water to release hydrogen gas and can be cut with a knife. They are also malleable and ductile unlike the lanthanides which are more brittle. Most of. the elements are silver colored and solid at room temperature. Actinides have a wide variety of uses in smoke detectors and also scientific and medical research due to their radioactive properties.

Terms in section

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


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


Brittle is used to describe a physical property where layers of atoms when moved across each other will break apart. Commonly in ionic lattices as the ions repel each other


Malleable describes when layers in a solid can slide over each other when a force is applied


Ductile is a term used to describe when layers in a metal can be pressured down into smaller layers that are next to each other turning them into a wire

Synthetic element

Synthetic elements are elements that do not occur naturally in the universe and have to be created in a lab or through nuclear experiments in a cyclotron


Isotopes are atoms of the same element with different number of neutrons and the same number of protons. React chemically the same but have a different masses


Decay is a process of the nucleus breaking down into two smaller nuclei and releasing a radioactive particle

Particle accelerator

A particle accelerator is a machine designed to speed up atoms before colliding them together to create new elements with a large mass


Radioactive is the term given to an element or substance that will release particles as radiation as it is unstable and begins to break down


Elements are atoms with the same number of protons in the nucleus


Actinides are elements from the atomic number 89 to 103 largely forming the F block of elements in the extended periodic table. They are mostly radioactive


The Lanthanides of the Expanded Periodic Table


Advanced Electron Configuration