graphite

-終場ソ使者-

delocalized electrons are electrons which are not bonded together, graphite can conduct electricity due to the free electrons(delocalized)
the electrons can move together and forms a special intermolecular force called instantaneous dipole-induced dipole attraction* between 2 layers.
but, instantaneous dipole-induced dipole attraction is one kind of weak van der Waals' forces, this attraction is not a main point for bonding,
in general cases, each carbon atom in a graphene has only 3 single bonds without any double bonds.

*instantaneous dipole-induced dipole attraction is beyond your standard, you may not need to understand now, there is no contradiction in your questions.
you can now consider the attraction between 2 graphenes is called van der Waals' force

john456

delocalized electrons are electrons which are not bonded together, graphite can conduct electricity  ...
-終場ソ使者- 發表於 17-11-2010 21:37

查實有冇strong van der waals' force....
好似e加次次都係講親都一定係weak van der waals' force....

-終場ソ使者-

van der Waals' force係intermolecular forces既一個統稱
係有strong既,eg: hydrogen bond,permanent dipole-permanent dipole attraction(is a polar bond),
不過你地而家唔洗知係咩黎住,microscopic world II會講

delocalized electrons係free electrons黎

[S]【YU】

Matter forms bond to make it become more stable.
carbon既世界入面,有一種比form死bond 更強既現象,叫做resonance. 即係你阿sir所講既情況.

好似Benzene咁,每粒C都要form 4個bond,就會出現圖中左邊既arrangement,但係個pi bond (double bond 中較弱既bond) 既電子可以跳黎跳去,變成圖中右邊咁既arrangement,所以就係所講既double bond有時變single bond, single bond 有時變double bond 既情況.
個pi bond跳黎跳去,就好似form左一個會轉既圈,呢個咁既樣比圖中左邊右邊都更穩定.
Bond其實係electons pairs,可以郁既bond => delocalized electrons

From wiki, Benzene



不過有delocalized electrons唔代表可以conduct electricity....我未聽過benzene可以通電...
graphite既resonant應該同benzene有分別.

-終場ソ使者-

Matter forms bond to make it become more stable.
carbon既世界入面,有一種比form死bond 更強既現象,叫做 ...
[S]【YU】 發表於 20-11-2010 01:15

pi bond係咩黎-.-


補充番,fullerenes(eg:C₆₀ buckminsterfullerene)都有delocalized electrons,不過佢唔能夠通電,因為佢只係一個simple molecular structure黎

[S]【YU】

諗返通.... Benzene, C60 既 delocalized electrons 都限制左喺1個molecule入面.
而graphite既structure係六角蜂巢陣,layer by layer,delocalized electrons可以喺layer與layer之間既空間自由活動,所以:
如果apply 電壓 parallel to layers,electrons係可以喺層layer上面drift黎通電
如果apply 電壓 perpendicular to layers,因為electons俾layer隔開,所以通唔倒電.


double bond兩個bond係有分別,pi bond 係 double bond 入面較弱既bond. 當你學到hybridization既時候,就會知係咩黎.
http://en.wikipedia.org/wiki/Double_bond