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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

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  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Sep 2 '21 at 15:58
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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 for the pentachloride and 440°C with decomposition 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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