Lewis structures can be used to understand why some...

Key Concepts

Coordinate (Dative Covalent) Bonding

Coordinate covalent bonding involves the formation of a bond where both electrons come from the same atom. This type of bonding is seen when a molecule with an electron deficiency, such as BH3, accepts a pair of electrons from another molecule like ammonia, thereby forming a stable adduct (BH3NH3) by effectively filling the electron-deficient atom’s valence shell.

Dimerization

Dimerization is the process in which two identical molecules combine to form a dimer, often resulting in greater stability. In the case of nitrogen dioxide (NO2) forming dinitrogen tetroxide (N2O4), the dimerization involves the pairing of unpaired electrons from two NO2 molecules, leading to a structure with all electrons paired and a more stable configuration.

Electron Deficiency

Electron deficiency refers to a situation where an atom or molecule has fewer electrons than required to complete its valence shell. This is critical for understanding reactivity; for example, boron in BH3 is electron deficient, which makes it a strong Lewis acid that readily accepts an electron pair from donors, such as ammonia.

Octet Rule

The octet rule is a guiding principle in chemistry stating that atoms tend to gain, lose, or share electrons to achieve a full valence shell of eight electrons, leading to more stable configurations. This principle helps in constructing accurate Lewis structures by ensuring that atoms either share or possess enough electrons to mimic noble gas configurations.

Lewis Structures

Lewis structures are diagrammatic representations of molecules that show how the valence electrons are arranged among the atoms. These structures help in visualizing bonds (both sigma and pi bonds), lone electron pairs, and overall electron distributions, which are essential for predicting chemical reactivity and understanding molecular geometry.

Transcript

00:01 So in this video, we're gonna talk about question 90 from chapter eight, which says lewis structures could be used to understand why some molecules react in certain ways.

00:09 Right? the liver structures with reactions and reactions and products and the reactions described below give a possible explanation for why these two reactions occur.

00:18 So in a weird given, nitrogen dioxide dime arises to produce die nitrogen tetroxide.

00:24 Um, so nitrogen dioxide that's one nitrogen atom into oxygen atoms in 02 and die nitrogen tetroxide.

00:32 That's two nitrogen atoms in four oxygen atoms into 04 so we have to, you know, to coming together to form into before.

00:41 So let's try drawing the louis structure for an 02 1st so we know that our nitrogen ana is gonna bring five valence electron, and each of our oxygen atoms will bring six, which will add together to give us a grand total of 17 electrons toe work with.

00:58 So we know where nitrogen atoms their central adam, um, what happens if we sing live on each of our oxygen atoms to it on and fill in the octet ce on the oxygen atoms? well, if i calculate my formal charges on that.

01:13 Um well, if i do that, then i have one electron left over, and i can put it on my nitrogen atom.

01:19 And if i calculate the formal charges on the structure for oxygen, remember formal charges are the number of valence electrons.

01:25 The adam usually has minus the number of electrons that aaron lone pairs around that adam minus half the number of electrons that aaron bonds to that adam.

01:34 So for these oxygen atoms, we have six valence electrons, minus six electrons and lone pairs minus one electron from half of the bond.

01:42 So that's a formal charge of minus one.

01:45 And then for my son's relented.

01:46 And adam, i have five electrons minus one electron in lone pairs minus two.

01:51 Two electrons from my bonds.

01:53 That's a formal charge of plus two.

01:55 So that's not a very good louis structure.

01:57 What if i draw both of my ox? jonathan's doubly bonded to my nitrogen atom on dhe.

02:03 Then i fill in the octave in my oxygen atoms.

02:05 I still have one electron left over, so i put it on my nitrogen atom.

02:09 Then my formal charges are six minus four.

02:12 Minus two equals zero for the oxygen atoms and five minus four minus one equals zero for the nitrogen atoms.

02:21 Um, so that's a pretty good loose structure.

02:23 Another one i could potentially draw is with a triple bond to one of my oxygen's in a single bond to the other.

02:29 That would give me a formal charge of zero on nitrogen, but then one of my oxygen autos will have a plus one formal charge, and the other one will have a minus one formal charge.

02:37 So it seems like the best lewis structure is the one where my oxygen atoms are both doubly bonded to my nitrogen atom.

02:46 Um, what about into oh, for well, we can basically just take to, you know, two's and stick them together.

02:54 Um, i noticed that my had just one electron on my nitrogen, adam, and you know, too.

03:01 So if i have to have him come together, the the single lone electron on each of my nitrogen atoms can come together to form a bond on.

03:11 So if i do this, i end up with this louis structure where i've just taken two of my eno to lewis structures and bonded them together and so my formal charges are all zero still on.

03:26 So we were told to give a possible explanation for why these reactions occur.

03:31 Well, this reaction this diamond ization, happens because you have a very unstable when we have a lone electron like this, just one of them rather than a pair we call a radical electron.

03:42 So when you have this radical electron, it's very reactive and will readily react with another in 02 to form a bond.

03:51 So, inbee, we have boren boron.

03:54 Try hydride.

03:57 Um, except a pair of electrons from ammonia warming.

04:01 Be age to be in aged three.

04:03 Well, boron, try hydride.

04:04 That's one boring adam and three hydrogen atoms...

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