For the indicated atom in each of the following molecules or ions, give the number and arrangeme

For the indicated atom in each of the following molecules or...

Key Concepts

VSEPR Theory

VSEPR (Valence Shell Electron Pair Repulsion) Theory predicts the three?dimensional arrangement of electron pairs around a central atom. It states that electron pairs, both bonding and non-bonding, will orient themselves as far apart as possible to minimize repulsion, thus determining the electron pair geometry and influencing the molecule's overall shape.

Electron Domain Counting

Electron domain counting is the process of identifying all regions of electron density, including bonding pairs and lone pairs, around a central atom. This method is key to applying VSEPR theory, as the number of electron domains directly determines the basic geometry (e.g., linear, trigonal planar, tetrahedral) about the atom.

Bonding Versus Lone Pairs

The distinction between bonding pairs, which are involved in bonds between atoms, and lone pairs, which are localized on a single atom, is crucial in molecular geometry. While both types contribute to electron pair repulsions, lone pairs exert greater repulsive force than bonding pairs, leading to adjustments in bond angles and overall molecular shape.

Transcript

00:01 In this question, we are looking at the arrangement of electron pairs around the atoms pointed out in molecules or ions.

00:11 So in part a, we're looking at arsenic in the arsenic ion.

00:17 So here we are going to have four oxygens, which have six valence electrons, plus we have a charge of negative three on this ion, which means that we are going to have three more electrons, each electron adds a negative charge of one.

00:37 And then arsenic itself has five valence electrons.

00:42 So here we are working with 32 electrons.

00:47 Now when we draw this out, we have arsenic as the central atom of the ion, surrounded by four oxygens, and an overall charge of negative three.

00:59 So each of these bonds around arsenic is two electrons.

01:04 We have two, four, six.

01:06 Six, eight.

01:07 We subtract that from 32 and we're dealing with 24 remaining electrons.

01:13 So we're going to add these around.

01:17 6, 12, 18, and 24.

01:26 However, arsenic has five alinous electrons, which means it has five electrons surrounding it.

01:35 So we're going to want to take away one of these lone pairs from an oxygen and add it into a double bomb.

01:42 So that the five valence electrons and arsenic all have a bonding partner.

01:48 And here in this question we are being asked about the number and arrangement of electron pairs around an atom.

01:56 And in arsenic here, we are going to have five electrons, electron pairs, and your arrangement is going to be in a tetrahedral.

02:15 Formation, while we do have a double bond present, we overall only have four places in space where electrons are existing, which means that we're going to be having a tetrahedral geometry.

02:28 And since all of these four domains have bonding electrons, our structure is tetrahedral.

02:35 Now, if we look at part b, we are dealing with selenium in selenium 042 minus.

02:42 Selenium has six valence electrons.

02:46 We have four oxygens with six valence electrons, and then we have this charge of negative two, which means two more electrons are being handled.

02:54 So this is ultimately going to get us to 32 electrons...

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