Man Lai 發問於 科學及數學化學 · 9 年前

# Drawing of complex compound

Recently, i met problem drawing complex compound, i would use (NPCl)2 as an example.

While questions require me to draw the outermost shell electrons of this compound, it is hard for me to decide which atom should the be center atom. The correct answer of the question should be one double bond between P and N, and a single bond with another N.

It's hard for me to decide where i should put the Cl atoms and forming the ring structure.

Any hints or rules about drawing similar compounds?

Thanks!

It should be (NPCl2)3 instead of (NPCl)2

### 1 個解答

• 最愛解答

Is there a typo?

Is it (NPCl2)3 or anything else instead?

2012-02-12 17:29:55 補充：

For (NPCl2)3, its structure is as follow :

It can be found on wiki.

It is a trimer of NPCl2.

To deduce the structure of these kinds of compounds(diimer/trimer/...),

we can first count the number of bonds that commonly can be formed by the atoms.

Use (NPCl2)3 as example,

Nitrogen: 3

Chlorine: 1

Phosphorus: 3

the one that forms most bonds is usually the center atom.

However, in this case, N and P is the same.

So, we can see the less common forms,

P sometimes can form 5 bonds while N cannot(because of the orbital stuff).

So, we would use P as the center atom.

Then, draw the easiest ones, Cl, first, we can have

Next, we add N(no matter single bond or double bond because when repeating, it will be just the same)

We may have

Last, repeat it.

The key is to find out the center atom and the number of bonds it forms.

As metioned above: use the atom that can form most bonds, normally, as the center atom.

("normally" means not to concern the special cases like Cl can form up to seven bonds in ClO4-/N can form up to four bonds in NO2+/etc.)

While encountering cases that there are same ones(P and N), determine the possibility of atoms to hybridize and form more bonds. But still "common" is very important, do not concern the extremities.