Transition metals often form complex bonds that can have both ionic and covalent character. To confirm the bond type between a transition metal and a nonmetal like B or N using a paper-based method, first examine the electronegativity difference: a significant difference (greater than 1.7) suggests ionic bonding, while a smaller difference indicates covalent bonding. Then, analyze bond lengths and energies from crystallographic data or spectroscopy; shorter, stronger bonds typically indicate covalent character. Additionally, use spectroscopic techniques such as IR or Raman to study vibrational modes, and XPS to examine electronic environments. Lastly, compare the compound's properties (e.g., solubility, conductivity) with known ionic and covalent compounds to draw parallels. Combining these steps will help confirm whether the bond is predominantly ionic, covalent, or a mix of both.

It depends on which metal and non-metal you are talking about.

Metal-non-metal bonding can be polar covalent, non-polar covalent, ionic or even coordinate.

If the electronegativity difference is less or more or less comparable, bonds can be polar or non-polar covalent bonds. If the electronegativity difference is very huge it will be ionic and if one is Lewis acid, an electron deficient with a vacant orbital in the valence shell and the non-metal is electron rich, there can be coordinate covalent bond and that depends on whether you talking about non-metal, which is atom, molecule or an ion.

Please read about structure and bonding aspects in any standard Inorganic Chemistry book that deals with structure and bonding concept.

With best wishes

Balakrishna

Thank you Chuanzhao for putting this important questions.

Aneeza pointed out how to approach the question: EN difference. Thank you.

I would start more fundamentally:

1) there is a continuum of bonds in between completely unpolar covalent (e.g. H-H) to very polar covalent (e.g. H-Cl) or ionic*. The EN difference gives an idea how polar the bond is.

2) A big problem in this approach is, that while for completely covalent bonds, there are many examples: H-H, C-C, P-P, Mn-Mn, etc. there is no example of a pure ionic bond*. Even NaCl has a ~20% covalent contribution to the overall ~80% ionic interaction.

3) The next problem is, that we should not compare molecules with solid state compounds. If we take only molecules, the covalent bonds range from completely unpolar to very polar covalent. Exceptions are ion pairs - which are kind of molecules. But also ion pairs do not have a 100% ionic interactions. There is always covalent and van der Waals (dispertion) in addition to ionic forces in them.

4) For solids we should carefully think about if the description of individual bonds makes any sense: ionic-covalent-metallic? Solids form band structures. They do not have individual bonds.

5) coordinative bonds are = polar covalent bonds. Anything else is a misconception.

So, a simple definition can be done along the EN difference, but the type of material (molecules, ion pairs, solids) must be considered.

But now for my question to you all:

Can you think of experimental methods to find out which type of bond is present in a specific molecule?

Best

AK