Comparing covalent characters of two halides of group 15

Which is more covalent : NCl3 or PCl5 and why?
This question was asked on a test, and the given answer was NCl3. Shouldn’t PCl5 be more covalent since pentahalides are more covalent than trihalides?[![enter image description here](https://i.stack.imgur.com/xyRL7.jpg)](https://i.stack.imgur.com/xyRL7.jpg)




Pentahalides are more covalent than trihalides **of the same element with the same halogen**. For instance $\ce{TaCl5}$ is more covalent than $\ce{TaCl3}$ (the respective WP articles give their melting points as [216°C](https://en.wikipedia.org/wiki/Tantalum(V)_chloride) for the pentachloride and [440°C with decomposition](https://en.wikipedia.org/wiki/Tantalum(III)_chloride) for the trichloride); but we cannot make such a simple comparison of $\ce{TaCl5}$ with either $\ce{TaBr3}$ or $\ce{PCl3}$. Similarly the pentahalide/trihalide rule could be overriden by the difference between nitrogen and phosphorus in your case.


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