Lists of metalloids cluster. Cluster 1 (93%) = B, Si, Ge, As, Sb, Te; cluster 2 (44%) = Po, At; cluster 3 (24%) = Se; cluster 4 (9%) = C, Al; cluster 5 (5%) = Be, P, Bi; cluster 6 (3%) = Sn; and cluster 7 (1%) = H, Ga, S, I, Pb, Fl, Mc, Lv, Ts. The resulting geometric trend line has the formula y = 199.47e and an R value of 0.9962. The elements commonly classified as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. The status of polonium and astatine is not settled. Most authors recognise one or the
Nonmetal with the same tetragonal structure as tin; when decompressed—and depending on the speed of pressure release—metallic germanium forms a series of allotropes that are metastable at ambient condition. Germanium also forms a graphene analogue, germanene. Arsenic and antimony form several well known allotropes (yellow, grey, and black). Tellurium is known only in its crystalline and amorphous forms; astatine is not known to have any allotropes. Hydrogen and helium are estimated to make up approximately 99 per cent of all ordinary matter in the universe. Less than five per cent of the Universe is believed to be made of ordinary matter,