Melting and boiling points of titanium tetrahalides

[i_love_science]

Homework Statement

The melting and boiling points of the titanium tetra- halides are given in the table (see below). Rationalize these data in terms of the bonding in and the intermolecular forces among these compounds.

Relevant Equations

bonding
intermolecular forces

Table

	boiling point (°C)	melting point (°C)
TiF4	284	N/A
TiCl4	-24	136.5
TiBr4	38	233.5
TiI4	155	377

The solution says that TiF4 is an ionic compound, while TiCl4, TiBr4, and TiI4 are covalent compounds. How would I determine this from the problem without prior memorization/knowledge? Thanks.

 

[Borek]

What do you know about general rules of boiling/melting points of ionic and covalent compounds?

 

[epenguin]

Table

	boiling point (°C)	melting point (°C)
TiF4	284	N/A
TiCl4	-24	136.5
TiBr4	38	233.5
TiI4	155	377

We all have something to learn, and I had never met before compounds whose melting points were higher than their boiling points, have I missed something?

 

[Astronuc]

We all have something to learn, and I had never met before compounds whose melting points were higher than their boiling points, have I missed something?

It would appear that the column titles are switched.

Homework Statement:: The melting and boiling points of the titanium tetra-halides are given in the table (see below). Rationalize these data in terms of the bonding in and the intermolecular forces among these compounds.
Relevant Equations:: bonding
intermolecular forces

Table
boiling point (°C)melting point (°C)TiF4284N/ATiCl4-24136.5TiBr438233.5TiI4155377

Check the information in the Table. Various sources, including supplier websites, have the melting point of Ti(IV)fluoride as 377° C (710.6° F), and it sublimes.
https://www.americanelements.com/titanium-iv-fluoride-7783-63-3
https://www.americanelements.com/titanium-iv-iodide-7720-83-4

 

[i_love_science]

What do you know about general rules of boiling/melting points of ionic and covalent compounds?

Ionic compounds have higher boiling and melting points than covalent compounds. Is there a specific mp or bp value above which compounds are considered ionic?

It would appear that the column titles are switched.

They're actually not switched, this is the exact question.

 

[Borek]

Ionic compounds have higher boiling and melting points than covalent compounds.

OK

Is there a specific mp or bp value above which compounds are considered ionic?

No, but as the rule is only approximate there is no way to define such temperatures (plus, there are no such things as purely ionic or purely covalent compounds, each bond has some mixed properties). However, it works quite well when you have a series of analogous compounds that can be easily compared. That's the case here, do you see any anomaly in the data?