## 4 ligands shape?

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Rebecca Chu 1C
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Joined: Fri Apr 06, 2018 11:02 am

### 4 ligands shape?

I know 4 ligands can either be a tetrahedron or square planar, but how am I supposed to tell which shape is which when there are 4 ligands?

Kara Justeson 1B
Posts: 31
Joined: Fri Apr 06, 2018 11:03 am

### Re: 4 ligands shape?

I might be wrong, but I thought we didn't have to know how to tell the difference for this class. Based off what I understood from lecture I think we were just supposed to know that both types have four ligands.

Mariah Guerrero 1J
Posts: 32
Joined: Fri Apr 06, 2018 11:03 am

### Re: 4 ligands shape?

Square planar has four ligands and two lone pairs. A difference between the two is that the bond angles of the square planar shape are smaller than 109.5 because the atoms are pulled closer together by the repulsion of the lone pairs.

NatalieSDis1A
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Joined: Fri Apr 06, 2018 11:05 am

### Re: 4 ligands shape?

I read in the book that square planar is usually formed when the central metal atom has d8 electron configuration. So that's why Pt2+ and Au3+ have the square planar complex.

Michael Park
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### Re: 4 ligands shape?

I don't think we need to know the difference between those two structures, only that they have 4 ligands attached to the central atom.

YeseniaGomez_1L
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### Re: 4 ligands shape?

I suggest you first figure out the Lewis structure then see if the 4 include any lone pairs, if there is a lone pair it is a square planar and so the angles are different, becuse the lone pairs decrease it through repulsion.

breannasung_1K
Posts: 30
Joined: Fri Apr 06, 2018 11:05 am

### Re: 4 ligands shape?

When we want to know just the general shape of the structure, we have to consider all regions of electron density, including lone pairs. Many times, when there are 4 regions of electron density the shape is tetrahedral. When we want to know the molecular structure, we have to consider how the lone pairs affect bond angles and those bond angles may contribute to the square planar shape (4 ligands and 2 regions of electron density).

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