Chemistry Lesson 1
Atomic and Molecular Structure (Grades 9-12)
|LANTHANIDE, ACTINIDE, TRANSACTINIDE, AND TRANSURANIUM ELEMENTS|
There are 2 rows that are set apart from the main Periodic Table of the Elements so that they don’t make the grid too wide.
The last row of elements consists of the Actinides, from actinium (Ac #89) to nobelium (atomic number 102), which should be placed on row 7. Actinides are so rare as to be of little interest except for Uranium (U) and Plutonium (Pu) which are used in nuclear reactors.
Which reminds us – all elements larger than bismuth (Bi, atomic number 83) are radioactive, and given enough time (in some cases, billions and billions of years, for some they’re gone in less than a second), will completely disappear from the universe. There are also some radioactive forms of the other elements.
Transactinide and Transuranium
The elements larger than uranium (atomic number 92) are considered transuranium elements. http://web.fccj.org/~ethall/uranium/uranium.htm
Twenty-four of these elements, up to and including atomic number 116, have been discovered. Eleven of them, from neptunium through lawrencium, belong to the actinide Actinide series. The other thirteen, which have atomic numbers higher than 103, are referred to as the transactinides. All the transuranium elements are unstable, decaying radioactively with half-lives that range from tens of millions of years to mere fractions of a second. Since only 2 of the 20 have been found in nature (neptunium and plutonium) and those only in trace amounts, the synthesis of these elements through nuclear reactions has been an important source of knowledge about them.
There is a group of 17 metals that are designated as Rare Earth Elements. The 17 elements are scandium (atomic number 21), yttrium (atomic number 39), and the lanthanides (atomic numbers 57 to 70), including lutetium (atomic number 71). Promethium (atomic number 61) shouldn’t be included since it does not occur naturally on earth. Some people may also include the actinides, but only 3 of them exist naturally.