During the borax bead test, heating forms a transparent glassy bead. When this bead is heated with a — p Block Elements Chemistry Question

💡 Solution & Explanation

Upon heating, borax loses water and melts into a glassy bead consisting of sodium metaborate ($NaBO_2$) and boric anhydride ($B_2O_3$). The basic transition metal oxide ($CuO$) reacts with the acidic $B_2O_3$ to form a colored metal metaborate, which is Copper(II) metaborate or $Cu(BO_2)_2$ (blue).