Q.The compound that is used in nuclear reactors as protective shields and control rods is

Boron is the sole non-metal of group 13 and is comparatively unreactive at ordinary temperature, though it becomes reactive at high temperature. Much of its chemistry is electron-deficient covalent bonding, a consequence of its small size, high ionisation energy, and an electronegativity close enough to carbon's and hydrogen's own to favour genuinely covalent bonds with both.

Every metal except the alkali metals reacts directly with boron to form a boride (general formula MₓBᵧ); boron does not react with hydrogen directly but its hydrides (boranes, e.g. diborane) are made indirectly instead; at high temperature it combines with halogens to give boron trihalides, with dinitrogen to give boron nitride, and with oxygen (around 900 K) to give its oxide, B₂O₃. Ordinary halo acids do not react with boron at all, but strongly oxidising acids (sulphuric, nitric) do, giving boric acid; boron also reacts with fused sodium hydroxide to give sodium borate. …