The following pictures represent structures of the hydrides of four second-row elements:

(1)

(2)

(3)

(4)

(a) Which compound has the highest melting point?

Video transcript

All right. Hi, everyone. So for this question, let's consider the following hydris of third row elements where the white spheres represent hydrogen. And here we have four such hydrates, determine which compound or determine the compound with the highest melting point. Option A says compound one. Option B says compound two. Option C says compound three and option D says compound four. Now recall that generally speaking, there are three different types of hydris. We have ionic hydrates, covalent hydride and interstitial hydride. Now, the melting or boiling point of a given substance is dependent on the strength of that compound intermolecular forces or IMF s for short right now, generally speaking, the stronger the IMF the more energy is required to break it during the phase transition resulting in a higher melting or boiling point. Now recall first and foremost that an ionic hydride features an ionic bond between hydrogen atoms and metallic elements, covalent hydride. On the other hand, feature covalent bonds between hydrogen atoms and nonmetals. Now, for covalent hydride, the ratio of nonmetal atoms to hydrogen depends on the group in which that nonmetal resides in. However, the interstitial hydride generally form between hydrogen and transition elements in which hydrogen fills in the so-called gaps or interstices between the metal atoms themselves. And the first thing I want to point out here is that compounds 12 and four, 12 and four are all examples of cove and hydrate. And the reason for this is because the white spheres that represent hydrogen are all surrounding the central atom indicating that they're being connected to the central atom via a covalent bond. However, compound three does not display this pattern because notice how there's a sort of alternating pattern between hydrogen and the other element. Now, this alternating pattern indicates that compound three is actually an ionic hydride. Because by arranging the C and the anion in this alternating pattern, you ensure that all cat ions are surrounded by anions and vice versa, right? Because recall that in an ionic hydride, hydrogen or hydride is the anion. And so with this in mind, because ionic bonding is stronger than co Whitland bonding, more energy is required to break an ionic bond compared to an a covalent one, which means that ionic hydride are going to have a higher melting point than a covalent hydride. Therefore, right, because compound three is the only ionic hydride listed, our answer is going to be option c in the multiple choice because compound three is going to have the highest melting point. And with that being said, thank you so very much for watching. And I hope you found this helpful.