Actinium

Actinium is a chemical element, having the chemical symbol Ac.

Actinium 227   Ac 89 [Rn] 7s2 6d1 [ ? ] Transition metal:

Its atomic number (the number of protons) is 89. It has a Standard Atomic Weight of 227, and is typically found as a solid in its elemental form.

Actinium is considered to be a member of the "Transition metal" class of elements, has a boiling point of 3,198 °C, and a melting point of 1,051 °C.