See explanation below.
Work Step by Step
Toxic metal that lies between to other toxic metals? Thallium. Component of heat-resistant (Pyrex-type) glass This is Boron (but could also be aluminium as it contains both) Largest temperature range for liquid state of an element? This is Gallium. Manufacture of high-speed compouter chips? This is Gallium Mild antibacterial agent (e.g. for eye infections)? This is boric acid Elementary substance with three-center, two-electron bonds? This is boron oxide. Metal protected from oxidation by adherent oxide coat? This is Aluminium.