# Determining central atom in NCl3

Less electronegative atom is the central atom. $\ce{N}$ is more electronegative than $\ce{Cl}$ as $\ce{Cl}$ has larger atomic radius. So why in $\ce{NCl3}$, $\ce{N}$ is the central atom?

But I wouldn't say it's an absolute rule that the less electronegative atom is central. For example, $\ce{NH3}$ has the N central and $\ce{Cl_2O}$ has the O central.
• Acc. to Pauling's scale, both have electronegativity 3.0 but as $\ce N$ has lesser atomic radius,it is more electronegative.But here it seems contradiction as a lesser electronegative atom ought to be the central atom.But it is also accurate that in nitrogen tri chloride , nitrogen is the central atom .Is the 'less electronegative atom is the central atom ' a wrong concept? – user5764 Jun 15 '14 at 1:59
• @user36790 I would say that the example of Cl and O basically proves there is no simple set of rules, since Cl can be in the center for chlorate, perchlorate and other compounds, while $\ce{Cl_2O}$ has the O central. Also, the symmetrical choice or lone atom in the center, isn't always correct as there is NNO. The rule "H is never in the center" you can usually count on, although a hydride can bridge two metal or boron atoms. I would say that carbon and nitrogen tend to be central slightly more than their electronegativities suggest and halogens non-central. SeCSe, CAt4, NI3. – DavePhD Jun 16 '14 at 12:11