The lanthanoids are sometimes simply called the rare earths, although strictly the ‘earths’ are their oxides. Nor are they particularly rare: they occur widely, usually together. All are silvery very reactive metals.
The recommended name for the group of elements from atomic number 57 (lanthanum) to 71 (lutetium). The traditional names are lanthanides, lanthanons, and rare-earth elements.
This subheading includes compounds of metals of the rare-earth series, called lanthanides (since lanthanum is its first element), which include the oxides of europium, gadolinium, samarium and terbium (terbite), which are used as neutron-absorbers in the control or safety rods of nuclear reactors and in colour television tubes.
