Anthem Blue Cross and Blue Shield is the trade name of: In Indiana: Anthem Insurance Companies, Inc. In Kentucky: Anthem Health Plans of Kentucky, Inc. In Missouri (excluding 30 counties in the Kansas City area): RightCHOICEÂ®. Managed Care, Inc. (RIT), Healthy AllianceÂ® Life Insurance Company (HALIC), and HMO Missouri, Inc. RIT and certain.
Astatine (At), radioactive chemical element and the heaviest member of the halogen elements, or Group 17 (VIIa) of the periodic table.
So I guess technically Astatine and Francium is the rarest natural element on the earth that exists. Technetium and Promethium should exist but they don't, so in a sense that would make them rarer. Astatine and Francium have been produced synthetically but it is hard to do because of the short half-life.