Figure 13.

A possible form of the periodic table of the elements at a pressure of three million atmospheres. This table is not yet complete—for example, elemental fluorine and a few others are not yet accessible—but note the absence of the traditional diagonal demarcation separating metals from non-metals (grey backgrounds) under normal conditions. The elements C, F, Cl, Ne, Ar, Kr and He have not yet been investigated at sufficiently high pressures to achieve metallization. We show here hydrogen as a metal; this reflects the situation for fluid hydrogen at these high pressures. In stark contrast, solid hydrogen does not attain metallic status, even at three million atmospheres imposed pressure (modified from [44]).