Chemistry- Covalent Bonding
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Anyone have dot-and-cross diagrams for these covalent bonds?
1) HCl
2) Ethane C2H6
3) Ethene C2H4
4) Carbon Monoxide CO
5) Sodium Nitrate NaNO3
6) Lithium Hydroxide LiOH
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Originally posted by Only-Way-4-Destiny!:
Anyone have dot-and-cross diagrams for these covalent bonds?
1) HCl
2) Ethane C2H6
3) Ethene C2H4
4) Carbon Monoxide CO
5) Sodium Nitrate NaNO3
6) Lithium Hydroxide LiOH
google is ur fren u know... if nobody post later then i post image...
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Seriously you're the first I know who asked for dot-cross diagram for HCl....
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psps. i accidentally added HCl over here. That i can draw myself. Sorry. I juz need to see some diagrams for Ethene, Ethane and Sodium Nitrate. Not so sure on how to draw those complicated ones
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LOL, HCl...
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yes i know. LOL
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Originally posted by Only-Way-4-Destiny!:
psps. i accidentally added HCl over here. That i can draw myself. Sorry. I juz need to see some diagrams for Ethene, Ethane and Sodium Nitrate. Not so sure on how to draw those complicated ones
You're also the first person I know asking for ethane.
Normally the teacher would show methane, and then proceed to show ethane as a 2nd example what....
I mean nobody would give octane or butane as a 2nd example what....
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Teacher only ask us to draw methane. Bo give ethane.
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Am i right to get a symmetrical shape when drawing ethane and ethene? I checked the electronic config by covering up the H atoms and counted the no. of valance electrons for C. It gives me a octet electronic config. And when i look at the H atom, it gives me a duplet electronic config. So am i right?
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Carbon Monoxide is not your syllabus. Because it got dative bond. Sodium Nitrate not require at your level too.
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Originally posted by Only-Way-4-Destiny!:
Am i right to get a symmetrical shape when drawing ethane and ethene? I checked the electronic config by covering up the H atoms and counted the no. of valance electrons for C. It gives me a octet electronic config. And when i look at the H atom, it gives me a duplet electronic config. So am i right?
Yep... -
My "gay" chem teacher ask us to draw. Not so sure about what is dative bond. He already said beforehand that some of the covalent bonds have ionic bonds.
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i seriously need dot and cross diagrams for Sodium Nitrate, Carbon Monoxide and Lithium Hydroxide. The rest i can do.
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Originally posted by Only-Way-4-Destiny!:
i seriously need dot and cross diagrams for Sodium Nitrate, Carbon Monoxide and Lithium Hydroxide. The rest i can do.
LiOH and NaNO3 are the same.....ionic bonds........but in the case of NaNO3, you have to first draw NO3-, from there you should be able to tell the electron pairs relevant for the ionic bonds.... -
Sodium nitrate is an ionic compound if I'm not wrong.
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Yes, it is an ionic compound. But Nitrate is a covalent bond.
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Only-Way-4-Destiny!, you have a choice - either bo hiu / bo chap your teacher, and don't bother about drawing structures of compounds that you won't be asked to draw at 'O' levels (assuming you *are* at 'O' levels... are you?), or if you want to learn them, then self-educate (this is the age of the internet - google be thy sword, wikipedia be thy shield) yourself about Kekule structures, Lewis structures, lone pairs of electrons, bond pairs of electrons dative covalent bonding, etc.
You can also easily google the structures of any compound you want. But it makes more sense, if you learn the underlying principles, so you can make sense of the structure you google out.
You may or may not understand the following (its ok if you don't, it's not required at 'O' levels anyway... you *are* 'O' levels, right? If you're 'A' levels, then you definitely must know how to draw the Kekule and dot-and-cross structures that your teacher tasked you), which is the reasoning and thought process that 'A' level students have to do go through, in drawing structures like the polyatomic nitrate(V) anion.
To draw the nitrate(V) or (NO3)- ion (it's recommended the student draw the Kekule structure first, then translate to dot-&-cross notation) :
1) First draw the central atom, N.
2) Then draw 3 O atoms, single bonded to it.
3) The fact that the anion is uninegative, means at least one of the O atoms must be negatively formal charged.
4) In other words, that O atom must have 3 lone pairs and one bond pair.
5) Hence, try drawing 1 single bonded O, and the 2 other O atoms be double bonded to N.
6) But in which case, N has violated its octet. Being in period 2, it does not have empty 3d orbitals with which to expand its octet.
7) Consequently, you realize that 2 of the O atoms must be single bonded (ie. each with 3 lone pairs and 1 bond pair).
8) Consequently in turn, you realize that the N atom must have a postive formal charge, because
8ai) you have 4 bond pairs for N, ie. 4 valence electrons near the nucleus of N, and indeed, N is in Grp V (ie. 5 valence electrons for no charge); so the N atom should indeed have a +ve formal charge.
8aii) the entire anion is uninegative, and since 2 of the O atoms have a -ve charge; so to cancel out the 2nd -ve charge, the N atom should indeed have a +ve formal charge.
8b) Since (ai) and (aii) agree with each other, this supports the validity of your Kekule structure.
9) Your N atom has trigonal planar electron geometry with sp2 electron orbital hybridization.
Once you've drawn your NO3- anion, with individual formal charges inside the brackets, and a overall uninegative charge outside the square brackets; draw the unipositive Na+ cation, also with square brackets. The electrostatic attraction between the cation and anion represent ionic bonding. So obviously, sodium nitrate(V) has ionic bonding between the cation and anion, but covalent bonding within the anion.
Hope you had fun. Everyone loves Chemistry!
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i m taking O levels next year. As i m in best class, my teacher pushes me a lot. Thx !
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Originally posted by Only-Way-4-Destiny!:
i m taking O levels next year. As i m in best class, my teacher pushes me a lot. Thx !
Keep up the good work then!
If you want more challenging practice questions, visit my thread here and attempt all questions designated as >>> 'O' Levels & 'A' Levels Qn (Challenging for 'O', Easy for 'A'). <<<
'A' & 'O' Level Chemistry Qns (A Collection)
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Originally posted by Only-Way-4-Destiny!:
i m taking O levels next year. As i m in best class, my teacher pushes me a lot. Thx !
Dude.....the ones you asked are really really basic. There's quite a looooong way, but its ok, there's time to learn. -
And in case you're still wondering how to draw carbon monoxide,
The dative (ie. "donated") covalent bond is from oxygen to carbon. Meaning, one lone pair from oxygen becomes a bond pair between oxygen and carbon.
Your Kekule or dot-&-cross structure should show :
Carbon having 1 lone pair and 3 bond pairs.
Oxygen having 1 lone pair and 3 bond pairs.
Hence, carbon has a -ve formal charge, and oxygen has a +ve formal charge.
This is due to the dative (ie. "donated") covalent electron bond pair; oxygen has lost an electron, carbon has gained an electron.
The reason why the dative bond occurs or exists, is to allow both C and O to have a stable octet.
For physical chemistry (but not organic chemistry*), reflect the nature of the dative bond with an arrow-headed line (as opposed to a normal line for a normal or non-dative covalent bond), for the Kekule structure.
For the dot-&-cross structure, the dative bond should be represented as xx or oo (where x or o represent electrons from oxygen), as opposed to xo or ox for a normal or non-dative covalent bond.
(* In O.C., curved arrows represent electron flow mechanism. And once the dative bond is formed, it is no different from any other covalent bond. Hence in O.C., you only show the formation of the dative bond using curved arrows; thereafter, normal lines to represent the bonds.
In P.C., the arrow-headed line to represent the dative bond, is actually the mechanism for the formation of the dative bond. If in the exam, you're unsure which diagram to submit (ie. you're unsure whether it's an O.C. or P.C. type question), do what the intelligent exam candidate would do - draw both alternative answers or forms, as long as both are correct, you'll get your marks.)