man made included.

I think that carbon (graphite, and diamond) has the highest boiling point. In fact, it sublimes. IIRC, this happens at temperatures between 5000 and 6000 C.

 

Maybe it is not the compound with the highest boiling point, but it certainly is among the compounds with the highest boiling point.

 

Of course, all this must be specified at atmospheric pressure. At much higher pressure, such as in the core of the planet Jupiter, even hydrogen can exist in solid or liquid state, while white-hot, with metal-like properties. But that is at a pressure of millions of earth's atmospheres.

i think covalent networks will have the higher melting points, but when the bonds break to become fluid, it will have different properties and boil instantly.

 

perhaps ionic compounds will have the higher boiling points.

 

the element with the highest melting/boiling point, i think, is tungsten.

 

slightly off topic, but are there conditions where helium is soild?

according to my data book, the real candidates of the elements would be:

 

Carbon (as Diamond) mp: 3823 bp: 5100

Tungsten: mp: 3650 bp: 5800

Rhenium: mp 3453 bp: 5900

 

all temps in Kelvin.

Some carbides have very high melting and boiling points:

 

ZrC mp 3500C, bp 5100C.

TaC mp 3800C, bp 5500C

 

Some substances with high melting point become soft like lead much before melting and others may start to react with oxygen and other gases even below 1000C. In practice graphite, carborundum (mp 2800C) and platinum (mp 1770C, bp 3800C) are often used where high heat occurs. Certain carbides and some oxides like Al2O3 (mp 2050C) and MgO (mp 2825C, bp 3600C) are also very common. Tungsten (mp 3420C, bp 5680C) and molybdenum (mp 2620C, bp 4630C) bear high heat very well but only in oxygen-free environment. There are also lot of special alloys that are incredibly strong at 1000C or 1500C but have lower melting points than their constituents.