Neptunium
thorium. the first is actinium (atomic number 89), and the second is thorium (atomic number 90)
Neptunium(Np)
Just buy the book a borders For $7:-)
Actinide series, a series of radioactive metallic elements in Group 3 of the periodic table. Members of the series are often called actinides, although actinium (Ac, atom no. 89) is not always...