Yttrium is a Block D, Group 3, Period 5 element. The number of electrons in each of Yttrium's shells is 2, 8, 18, 9, 2 and its electronic configuration is [Kr] 4d¹ 5s². In its elemental form Yttrium's CAS number is 7440-65-5. The yttrium atom has a radius of 177.6.pm and it's Van der Waals radius is 200.pm. Insoluble compounds of Yttrium are non-toxic, although water soluble compounds are somewhat toxic. Yttrium has the highest thermo-dynamic affinity for oxygen of any element. This characteristic is the basis for many of its applications. Yttrium is not found in nature as a free element and is almost always found combined with the lanthanides in rare earth minerals. While not part of the rare earth series, it resembles the heavy rare earths which are sometimes referred to as the "yttrics" for this reason. Another unique characteristic derives from its ability to form crystals with useful properties. Yttrium is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra high purity); metals in the form of foil, sputtering target, and rod, and compounds as submicron and nanopowder. Some of the many applications of yttrium include in ceramics for crucibles for molten reactive metals, in florescent lighting phosphors, computer displays and automotive fuel consumption sensors.Yttria stabilized zirconium oxide are used in high temperature applications, such as in thermal plasma sprays to protect aerospace high temperature surfaces and as an electrolyte in solid oxide fuel cells. The name Yttrium originated from a Swedish village near Vaxholm called Yttbery where Yttrium was discovered. Crystals of the yttrium-iron-garnet (YIG) variety are essential to microwave communication equipment. The phosphor Eu:Y2O2S creates the red color in televisions. Crystals of the yttrium-aluminum-garnet (YAG) variety are utilized with neodymium in a number of laser applications. Yttria can also increase the strength of metallic alloys. Yttrium was first discovered by Johann Gadolin in 1794. See Yttrium research below.

Cerium is a Block F, Group 3, Period 6 element. The number of electrons in each of Cerium's shells is 2, 8, 18, 19, 9, 2 and its electronic configuration is [Xe]4f² 6s². In its elemental form cerium's CAS number is 7440-45-1. The cerium atom has a radius of 182.5.pm and it's Van der Waals radius is 181.pm. Cerium is moderately toxic. Cerium is one of the products manufactured and distributed under the tradename AE Rare Earths. Cerium is the most abundant of the rare earths metals. It is characterized chemically by having two valence states , the +3 cerous and +4 ceric states. The ceric state is the only non-trivalent rare earth ion stable in aqueous solutions.It is, therefore, strongly acidic and moderately toxic. It is also a strong oxidizer.The cerous state closely resembles the other trivalent rare earths. The numerous commercial applications for cerium include metallurgy, glass and glass polishing, ceramics, catalysts, as the electrolyte for solid oxide fuel cells when doped with yttrium, gadolinium or samarium and in phosphors. In steel manufacturing it is used to remove free oxygen and sulfur by forming stable oxysulfides and by tying up undesirable trace elements, such as lead and antimony. It is considered to be the most efficient glass polishing agent for precision optical polishing. It is also used to decolor glass by keeping iron in its ferrous state. The ability of cerium-doped glass to block out ultra violet light is utilized in the manufacturing of medical glassware and aerospace windows. It is also used to prevent polymers from darkening in sunlight and to suppress discoloration of television glass. Cerium was first discovered by W. von Hisinger in 1903. The element was named after the asteroid Ceres. See Cerium research below.