4. They are thus made to come in below lanthanum and cerium and before tantalum. RADIOACTIVE ELEMENTS. The discovery of the radio-active elements has naturally led to the question as to what ...

But a little consideration must show this to be untenable. It is possible to apply electroscopic tests to the radioactive elements capable of estimating their amount with an accuracy of ...

Radioactive Elements.—The continuity of the periodic line thus established, the next question is the limits of this line. This found its answer by the second great discovery, namely the ...