24 replies to this topic

[Random]

So I'm taking AP Chem, and I'm doing decently so far, most of my test mistakes have been careless, but I really cannot get down Lewis Dot diagrams.

I understand everything, except the bonds.

For example, an NO2 Anion:
I draw it as an N with two single bonded O's, but it is really an N with a double bonded O, and a single bonded O.

How do you know when to do that

I know that it is because the N requires more electrons, but how do you know how many it needs?

[Cyo]

Use the periodical table duh. The rows and columns tell you how many electron layers and electrons and all that shit an atom has.

[Random]

Well I'm confused, because an anion of NO2 has the one double bond, one single, and two electrons on the N.
An anion of NO3 has one double bond, two single bonds, and no electrons on the N.

So the NO2 has 5 but the NO3 has 4?

[Cyo]

Well I'm confused, because an anion of NO2 has the one double bond, one single, and two electrons on the N.
An anion of NO3 has one double bond, two single bonds, and no electrons on the N.

So the NO2 has 5 but the NO3 has 4?

Yo man! You serious, man?

[Kyuu]

Um, I just woke up so what you're writing is confusing me. I'm just going to ignore all of it and try to explain it...using paint!

That's an NO₂^- right? Basically, it has N x1 = 5e-, O x2 = 12e-, and 1 e- to balance the charges which makes it an anion. First, draw the diagram and distribute the charges appropriately. There are 6 valence e- in the O on the left and it's sharing one bond. According to charge distribution, you count number of valence electrons and half the number of electrons in a bond (the O-N) bond, and that number of subtracted from the total number of valence electrons in the unbonded form of that element (6e- for O). N has 2 valence e- and 3 bonds, so that's a total of 5, minus 5 from that, which gives a charge of 0.

tbc...


Again for NO₃^- you count up the numbers and draw the structure. The bottom two O have a negative charge because they each have 6 valence e- and one bond, so that makes a total of 7 for charge. 6-7 = -1, so they both have a charge of -1. The top O has 4 valence e, 2 bonds, so that makes 6e-, subtracted from 6 so that has a neutral charge of zero. the N in the middle has 4 bonded e-, but the total number is supposed to be 5 to be balanced, so 5-4 = +1 so it has a positive one charge.

Edited by Kyuu, 28 October 2009 - 02:48 PM.

[Random]

Yo man! You serious, man?

Yeah. I'm retarded atm.

damn it's been a while since I've been in school... but this is pretty basic chem.. so I'll see if I can't try to remember/help you.

If I remember right, each bond represent 2 electrons... and a double bond represents 4 electrons because it is 2 electrons bonded to two others.

NO2 has a double bond (4 electrons) and a single bond (2 electrons) and since there is nothing else to bond to, it has 2 electrons on the left. NO3 has three bonds to make... so it makes 2 single bonds (4 electrons) and 1 double bond (4 electrons) which reaches the valent state for all elements.

At least... that's how I remember it.. and I was a chem major before I withdrew from uni fall of last year.

Hm, that clears it up a bit. Thanks

Um, I just woke up so what you're writing is confusing me. I'm just going to ignore all of it and try to explain it...using paint!

That's an NO₂^- right? Basically, it has N x1 = 5e-, O x2 = 12e-, and 1 e- to balance the charges which makes it an anion. First, draw the diagram and distribute the charges appropriately. There are 6 valence e- in the O on the left and it's sharing one bond. According to charge distribution, you count number of valence electrons and half the number of electrons in a bond (the O-N) bond, and that number of subtracted from the total number of valence electrons in the unbonded form of that element (6e- for O). N has 2 valence e- and 3 bonds, so that's a total of 5, minus 5 from that, which gives a charge of 0.

tbc...

I appreciate the effort you are putting in here

Um, I just woke up so what you're writing is confusing me. I'm just going to ignore all of it and try to explain it...using paint!

That's an NO₂^- right? Basically, it has N x1 = 5e-, O x2 = 12e-, and 1 e- to balance the charges which makes it an anion. First, draw the diagram and distribute the charges appropriately. There are 6 valence e- in the O on the left and it's sharing one bond. According to charge distribution, you count number of valence electrons and half the number of electrons in a bond (the O-N) bond, and that number of subtracted from the total number of valence electrons in the unbonded form of that element (6e- for O). N has 2 valence e- and 3 bonds, so that's a total of 5, minus 5 from that, which gives a charge of 0.

tbc...


Again for NO₃^- you count up the numbers and draw the structure. The bottom two O have a negative charge because they each have 6 valence e- and one bond, so that makes a total of 7 for charge. 6-7 = -1, so they both have a charge of -1. The top O has 4 valence e, 2 bonds, so that makes 6e-, subtracted from 6 so that has a neutral charge of zero. the N in the middle has 4 bonded e-, but the total number is supposed to be 5 to be balanced, so 5-4 = +1 so it has a positive one charge.

There's no like nitrite has 2 bonds and nitrate has 3,

How come I cant just put another two electrons on the O instead of making it a double bond? That's really all I don't get now.

[Kyuu]

How come I cant just put another two electrons on the O instead of making it a double bond? That's really all I don't get now.

Because compounds are more stable when they are neutral. Basically, in terms of stability, elements like these the most, in order:
1) To have an octet of e- surrounding them.
2) To have a neutral charge.

Let's take nitrate first of all. If you move the two e- to the oxygen, you only have 6e- surrounding N, AND the N has a +2 charge while all three O have -1 charges. This is less stable than the current form because you have a neutral O, and all of the elements have 8 e- surrounding them (an octet).

Does that make more sense?

Also, sparknotes has a pretty good section on it here. You can try reading that (especially since it also uses nitrite as an example) and see if it helps.

[Random]

the nitrogen would have two extra electrons just chilling as would the oxygen on the top in the diagram above. Electrons like to bond... so when they can, they do.

I'm fucking retarded.
I apologize for what I am putting you guys through.

Where would N get these two extra electrons if each O had 6 and a single bond?

[Kyuu]

Where would N get these two extra electrons if each O had 6 and a single bond?

Um, I'm not sure (why) it would need to? It depends on the compound and how it's balanced. It'd probably just share a double bond with O then because O with 6e and a single bond has a formal charge of -1.

But you'd need to list a compound. Otherwise it's pretty much irrelevant.

[Random]

Alright, thank you Kyuu and Cody

[Kyuu]

Basic chemistry is so much more fun than organic chemistry. Which is still fun.

But I hear pchem is a bitch and so is inorganic.

And if the chemistry program here weren't insane and I didn't fucking hate labs, I'd probably have been a chem major. But there's still a chemistry Nobel laureate who teaches at the public health school... I want to take classes with him!

How far did you get into your degree, Cody?

[Qwerty54]

I is a chemist.

You must have the easiest AP chem ever. And no offense, but if your only on this in november, you probably aren't gonna fair well on the AP exam.

[Sweeney]

I is a chemist.

You must have the easiest AP chem ever. And no offense, but if your only on this in november, you probably aren't gonna fair well on the AP exam.

I'm not an English professor.

But if you can't use fair/fare correctly, you must have the easiest job ever.

(Next time, contribute, or fuck off).

[Kyuu]

I thought he meant the "I is a chemist" thing sort of as a joke. But I caught the fair/fare thing. >_>

And, Cody, it's good that you're trying to get back into uni. A lot of people I know would've just given up so good on you. I hope you succeed.

I could personally use some time off from school but I doubt it's going to happen...

I have an orgo lab test on Friday at 9 in the morning so. Yeah. That'll be fun. At least it's a test about techniques and stuff and not an actual practical.

[Qwerty54]

I was joking in regard to "I is a chemist", though you caught me on the fair/fare. I really could care less about grammar on an internet board.

"(Next time, contribute, or fuck off)."


This is general chat. I believe I was adding to the discussion.

[Random]

I is a chemist.

You must have the easiest AP chem ever. And no offense, but if your only on this in november, you probably aren't gonna fair well on the AP exam.

You most likely live in a Western state, with an earlier school start date.
I've only been in school for about 35 days. We get fucked over on every AP.
I usually do fine, 4s and 5s on most so far.

[Kyuu]

We usually started in early Sept but... You guys start at the end of September? Or 35 business/school days?

Um, I'm pretty sure it's not a western state thing as I went to high school in Pennsylvania unless if you consider PA the far west. (Like the did in colonial times.)

[Random]

wow random.

When I was in high school we started early to mid August.

Yeah well we can go fuck ourselves I guess

We usually started in early Sept but... You guys start at the end of September? Or 35 business/school days?

Um, I'm pretty sure it's not a western state thing as I went to high school in Pennsylvania unless if you consider PA the far west. (Like the did in colonial times.)

I start Sept 15, but real class doesn't start till the 20th.

[Kyuu]

I got my organic chemistry test back today. yesterday I found out that my score was a 58 (booo), but then when I looked at the test, it appeared the TA had tallied up the score wrong and it was actually a 66 (which was the class average).

I then had to spend 3 minutes walking my TA over why it was a 66 and not a 64 (which he counted).

Fail.

But lol I feel a little better now since average is still better than below average.

[sealonfire]

I got my organic chemistry test back today. yesterday I found out that my score was a 58 (booo), but then when I looked at the test, it appeared the TA had tallied up the score wrong and it was actually a 66 (which was the class average).

I then had to spend 3 minutes walking my TA over why it was a 66 and not a 64 (which he counted).

Fail.

But lol I feel a little better now since average is still better than below average.

Chem is easy once u get the basics. It's just repeating the same thing again with more complicated stuff and memory work. Or at least the Chem I'm studying.

[Kyuu]

Are you studying organic chemistry? Mechanisms are kind of hard... you have to like, intrinsically understand them or they're not easy. Then they are.

Unless if your professor is an ass and makes the tests super hard. Which all of them here do.

[sealonfire]

You can go the other way. Memory, practice and you'll understand. Science related subjects at undergrad is not easy because certain things are discovered and the lecturers don't really have an explanation. So it's just one fine day and people discovered it and still trying to find the reason for it. You'll have to take it for granted for most stuffs you're learning and I suppose Organic Chem is one of them.

Look at the starting point and ending point, work your way there with the equations you've learned.

[BellaBleu]

Are you studying organic chemistry? Mechanisms are kind of hard... you have to like, intrinsically understand them or they're not easy. Then they are.Unless if your professor is an ass and makes the tests super hard. Which all of them here do.

Orgo is nothing in comparison to physical chemistry. Electron quantization is a lot tougher than mechanisms...

[Cataliste]

What I meant to say was that both nitrogen and oxygen would have a single electron each both fucking with their charge...

Chemistry done the NeoCodex way! Reminds me of the days when we used to have Physics debates on here. xD

/outb4offtopic

[Cataliste]

You making fun of my bullshit chemistry?

Remember when I was trying to find a way to make a drink that once metabolized would form amphetamine in the body? So that the energy drink would be a pro-drug for amphetamine, yet still legal?

I remember doing so much research with you and my chem professor trying to make it happen.

OMG man, we wasted WEEKS on that, lmfao. Jesus. You didn't happen to ever get that working, did you?