neon sign? Both helium and neon are in group 8A (also known as noble gases, but we'll get to that shortly). Elements are grouped together because they share similar properties, in part due to their electrons, specifically valence electrons. Elements have protons and neutrons in their nucleus, or center, and electrons in a cloud surrounding the nucleus.
The Representative Elements are those elements within the first two families (Groups I and II on the far left) and the last six families or groups (on the right) of the Periodic Table.
English chemist Charles Bury first used the word transition in 1921 when he referred to a transition series of elements during the change of an inner layer of electrons (for example n=3 in the 4th row of the periodic table).
partially filled d or f subshell in any common oxidation state. The term "transition elements" most commonly refers to the d-block transition elements. The 2B elements zinc, cadmium and mercury do not strictly meet the defining properties, but are usually included with the transition elements because of their similar properties. The f-block transition elements are sometimes known as "inner transition elements". The first row of them is called the lanthanides or rare earths. The second row consists of the actinides. All of the actinides are radioactive and those above Z=92 are manmade in nuclear reactors or accelerators.