Draw the Lewis structures for each of the following ions or...

Draw the Lewis structures for each of the following ions or molecules. Identify those that do not obey the octet rule, and explain why they do not:
(a) $\mathrm{SO}_{3}^{2-}$,
(b) $\mathrm{AlH}_{3}$
(c) $\mathrm{N}_{3}^{-}$
(d) $\mathrm{CH}_{2} \mathrm{Cl}_{2}$
(e) $\mathrm{SbF}_{5}$

Key Concepts

Incomplete Octet

An incomplete octet describes a situation where an atom does not achieve eight electrons in its valence shell, often seen in species that are electron deficient. This can contribute to higher reactivity, as the atom seeks additional electron pairs to reach a more stable electronic configuration.

Resonance Structures

Resonance structures are multiple valid Lewis structures for a single molecule or ion that differ only in the distribution of electrons, not the arrangement of atoms. They illustrate that the true electron distribution is a hybrid of these contributing forms, which is especially important for understanding the stability and bonding in species with delocalized electrons.

Expanded Octet

An expanded octet refers to the capacity of atoms in period 3 or higher to hold more than eight electrons in their valence shell. This phenomenon explains why some molecules, such as those involving central atoms like sulfur or antimony, can form stable structures with more than the typical eight electrons around the central atom.

Exceptions to the Octet Rule

Exceptions to the octet rule occur when atoms do not have eight electrons in their valence shell. These exceptions include species with incomplete octets, like electron?deficient molecules, and species with expanded octets, which are typically seen in elements in the third period or beyond that can accommodate more than eight electrons due to available d orbitals.

Octet Rule

The octet rule is a chemical guideline that atoms are most stable when they have eight electrons in their valence shell. This rule is a useful rule of thumb for predicting the bonding and structure of many molecules and ions, although there are notable exceptions.

Lewis Structures

Lewis structures are diagrams that show the arrangement of electrons among atoms in a molecule or ion. They represent bonds as lines between atoms and use dots to denote non-bonding electrons, helping to illustrate how atoms achieve stable electronic configurations.

Transcript

00:01 We have five lewis structures to draw, and then we're going to identify those that do or do not obey the octet rule.

00:10 So obey yes or no.

00:18 The first substance we're going to draw is the sulfite ion, s .o3, 2 -1.

00:26 And i went ahead and did the rule for this.

00:31 There are, for what we need for electrons, there are four electrons.

00:38 Each requiring 8, so we need 32 electrons.

00:46 For our half electrons, how many do we have? each one of these has 6, so it'll be 4 times 6 plus 2 for 26 electrons.

01:00 Excuse me.

01:02 That means i have 6 .32 minus 26.

01:05 It's 6 divided by 2 equals 3.

01:09 Each of the oxenge will have to be singly bonded to the s.

01:14 26 electrons.

01:35 And when i'm done doing this, you can count and check, and you will see that yes, this clearly obeys the octet rule.

01:50 Our second one that we're going to do is, let me look here, alh3.

02:01 Now aluminum has three valance electrons.

02:04 I'm going to draw aluminum's valence electrons in like this, sort of at a y.

02:10 I'm not very artistic.

02:14 Then hydrogen has a valence electron.

02:19 It's going to go like this.

02:21 Now i'm going to draw this again right here, down here a little bit, with lines, and you can see that in this structure, aluminum does not obey the octet rule, since it only has six electrons surrounding it.

03:09 And it would need eight to obey the octet rule.

03:15 That is our second one.

03:17 Our next one is n3.

03:20 This is the third one with a negative one charge...

Please give Ace some feedback