Which type (or types) of crystalline solid is characterized by ea...

Question

Which type (or types) of crystalline solid is characterized by each of the following? 
(b) softness, relatively low melting point;

Accepted Answer

Hey everyone, we're asked to identify the type or types of crystalline solid that possess the following properties, typically soft, relatively low melting point and poor electrical conductor. First we have a metallic solid. Now, as we've learned, we know, metallic solid is composed of metal with another metal or by itself and it is held by metallic bonds. So these are good conductors of heat and electricity. These are also lustrous, malleable and ductile, and they also have relatively low melting points. So even though a metallic solid has a low melting point, it is a good conductor of electricity. And we're trying to find the crystalline solid that is a poor electrical conductor. So A can't be our answer. Now let's go ahead and look at B for B. We have a molecular solid as we've learned, a molecular solid is held by inter molecular forces. So these are going to be typically soft. These also have relatively low melting points depending on the type of inter molecular force and these are also poor conductors of heat and electricity. So it looks like B is going to be our answer. But let's go ahead and assess C. So first see, we have an ionic solid as we've learned, an ionic solid is held by strong electrostatic attractions and these have a very high melting point. These are also poor conductors of heat and electricity, but it is a good electrical conductor in its molten form. So C is not our answer. So our final answer here is going to be be a molecular solid. Now I hope that made sense. And let us know if you have any questions.

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