Para cada molécula (a)-(f), indique quantas geometrias de domínio eletrônico diferentes estão de

Para cada molécula (a)-(f), indique quantas geometrias de...

Key Concepts

VSEPR Theory

The valence shell electron pair repulsion (VSEPR) theory is fundamental in predicting the three?dimensional arrangement of atoms in a molecule by considering the repulsions between electron pairs in the valence shell. It helps determine both the electron domain geometry, which includes bonding and non-bonding electron pairs, and how these domains influence the observed molecular geometry.

Electron Domain Geometry

Electron domain geometry refers to the spatial arrangement of all electron regions (both bonding pairs and lone pairs) around a central atom. This concept is crucial because different numbers of electron domains lead to distinct idealized shapes (such as linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral), and variations in the number of lone pairs can produce different hybridizations and affect molecular structure.

Molecular Geometry

Molecular geometry describes the arrangement of only the atoms in a molecule, excluding the lone pairs, and is derived from the electron domain geometry. It is important to understand that multiple electron domain geometries can result in the same molecular geometry if different combinations of bonding and lone pairs yield the same arrangement of atoms.

Bonding Pairs vs Lone Pairs

Differentiating between bonding electron pairs and lone pairs is essential because lone pairs occupy more space than bonding pairs and can alter bond angles. Although the underlying electron domain geometry might vary with different counts of lone pairs, the visible molecular geometry may remain the same, leading to scenarios where different electron domain configurations correspond to an identical molecular shape.

Transcript

00:01 If you're shown a molecule, you might not be shown all of the electron pairs, the lone pairs, around the central atom, which means that you might be able to have different electron domain geometries based on the molecular geometry.

00:18 So like for example, if you had something that looked like this, where you have three atoms all in a line, you have a molecular geometry that's linear, but linear can come from several electron domain geometries.

00:36 So, of course, linear can come from something that's linear, something that's going to have two electron domain domains.

00:45 And here, each one would be bonded.

00:46 But it could also come from something that has three lone pairs of electrons as well.

00:55 And in that case, you can get a linear substance if it's trigonal by pyramidal.

01:09 If you had five, if you had five electron domains.

01:17 If you have something, though, that looks more like this, let me just, that's exactly a 90 degree angle.

01:38 Well, this now, you've got something that's t -shaped.

01:43 And t -shape only comes from one possible molecular, the molecular geometry t -shape only comes from one possible electron domain geometry where you have two lone pairs of electrons here.

01:59 So that's also going to be trigonial.

02:02 By pyramidal.

02:13 Now, if you have something where you've got a central atom and you have six things coming off of it, six atoms, there's only one arrangement for that.

02:28 That is octahedral with six electron domains.

02:35 All of them are bonded.

02:37 So it's also the molecular geometry as well.

02:39 So we only have one possible electron domain geometry, octahedral...

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