Barium
Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Because of its high chemical reactivity barium is never found in nature as a free element. Its hydroxide was known in pre-modern history as baryta; this substance does not occur as a mineral, but can be prepared by heating barium carbonate.
Lanthanum
Lanthanum is a chemical element with symbol La and atomic number 57. Lanthanum is a silvery white metallic element and is the first element of the lanthanide series (or, on occasion, considered the first element of the 6th-period transition metals). It is found in some rare-earth minerals, usually in combination with cerium and other rare earth elements. Lanthanum is a malleable, ductile, and soft metal that oxidizes rapidly when exposed to air.
