Why is the aluminium boiling point higher than silicon? And why is silicon's melting point higher than aluminium?

Why is the Aluminium boiling point higher than silicon? And why is silicon's melting point higher than aluminium?

$$\ce{Si}$$ has 4 bonds which are covalent in nature. $$\ce{Al}$$ is metal thus possesses ionic bond.

Where have I not understood the concept?

• The concept itself does not seem to be awfully useful in predicting these differences. – Ivan Neretin Oct 23 '20 at 6:07
• You can't directly compare the melting of aluminum with the melting of silicon. Silicon converts from a nonmrtallic structure to a metallic one when it melts, aluminum is metallic all the time. – Oscar Lanzi Oct 23 '20 at 9:34
• For one aluminium does not for ionic bonds with itself; those are metallic bonds. – A.K. Oct 23 '20 at 19:30
• BTW, though the BP of Al is 2743 K, it's vapor pressure is fairly high at lower temps... see en.wikipedia.org/wiki/Aluminium . Thus, Al metalization is easily done in vacuo perhaps 1,000 K cooler. So BP is not quite so sharp, in this case. Now gallium is ab bit more extreme... – DrMoishe Pippik Oct 23 '20 at 20:14
• I'm afraid that the entire premise of the question is wrong. Both the melting point and the boiling point of Si are higher than than those of Al. Al: mp = 660 C, bp = 2519 C. Si: mp = 1414 C, bp = 2900 C. – theorist Oct 24 '20 at 4:14