(a) State whether or not the bonding in each substance is likely to be covalent: (i) glucose, (ii) nitrogen, (iii) aluminum hydroxide, (iv) ammonia, (v) neon. (b) A substance, XY, formed from two different elements, melts at \(350^{\circ} \mathrm{C}\). Is XY likely to be a covalent or an ionic substance?

In order to identify if the bonding in each substance is likely covalent, we can analyze the types of elements involved in the chemical. (i) Glucose (C6H12O6): Glucose consists of non-metal elements (carbon, hydrogen, and oxygen), and it is a molecular compound. Hence, its bond is covalent. (ii) Nitrogen (N2): Nitrogen is a diatomic molecule and consists of the same non-metal element (nitrogen). It forms a covalent bond with itself. (iii) Aluminum hydroxide (Al(OH)3): Aluminum hydroxide consists of a metal (aluminum) bonded to a polyatomic ion (hydroxide). This type of bond is ionic, so it is not covalent. (iv) Ammonia (NH3): Ammonia consists of non-metal elements (nitrogen and hydrogen) and is a molecular compound. Hence, the bond in ammonia is covalent. (v) Neon (Ne): Neon is a noble gas, and it has a full valence electron shell. Noble gases do not form bonds; therefore, there is no covalent bond in neon.

Substance XY is formed from two different elements and has a melting point of \(350^{\circ} \mathrm{C}\). Based on this information, we can determine whether XY is likely a covalent or an ionic substance. Ionic substances typically have high melting points (above \(300^{\circ} \mathrm{C}\)). So, since the melting point of XY is \(350^{\circ} \mathrm{C}\), it is suggestive that XY might have an ionic bond. On the other hand, covalent substances usually have lower melting points (below \(300^{\circ} \mathrm{C}\)). However, some covalent substances may have melting points slightly above \(300^{\circ} \mathrm{C}\). Given the melting point of XY and considering the historical melting points of known ionic and covalent substances, it is more likely that XY has an ionic bond rather than a covalent bond.