H-bond

2012-05-13 2:18 am
In Pauling scale
EN of Cl = 3.16
EN of N = 3.04
(from wiki)

Cl is more electronegative than N
but why N can participate in formation of H-bond while Cl cannot?


Thx!

回答 (5)

2012-05-13 3:43 am
✔ 最佳答案
氫鍵形成的條件是H帶很正的部分正電荷,另一原子帶很負的部分負電荷
所以一般情況下用EN差就可以預測分子是否會有氫鍵
因為EN差大,就會達到呢個條件,如HF,H2O,NH3所以真實解釋是否有氫鍵是用H帶很正的部分正電荷,另一原子帶很負的部分負電荷
而非只是EN差
氫鍵就像離子鍵
HF(-)--(+)HF ,只是電荷不完整而HCl中Cl 體積大,部分負電荷會被有效地分散(吸力削弱),所以就算Cl有較大的EN,但是較大的體積影響比這影響更大,所以以致Cl的部分負電荷不足以形成氫鍵

2012-05-14 18:29:10 補充:
Cl 電子有效地分散=3s & 3p電子層空間較大,電子密度較少->對帶正電荷物質吸引力減弱?
嗯 你可以這樣理解
參考: my
2012-05-16 6:35 pm
It is NOT strong enough.

It is correct that Cl is quite electronegative too.

It is also correct that there is uneven distribution of electron cloud in HCl as well.
But, compared to NH3 or HF, it is not so strong that we regard its intermolecule attractive force as "H bond".
2012-05-16 12:15 am
Re rooney10:你究竟喺度講緊乜嘢=,=
2012-05-14 7:03 pm
* 從EN角度睇, 要有H-BOND既條件係2隻ELEMENTS既DIFFERENCE IN EN VALUES夠唔夠大, 因為CL 同H既EN值相差還未夠大, 所以冇H-BOND. 哩個係以前係學校成日聽到既解釋.

* H-N ---- H-N, ''-''係COVALENT BOND ''----''係H-BOND = INTRAMOLECULAR FORCE. COVALENT BOND必定強過INTRAMO:ECU:AR FORCE

2012-05-14 11:22:36 補充:
* INTRAMOLECULAR FORCES有以下幾種:
1. HYDROGEN BOND
2. DIPOLE-TO-DIPOLE FORCE/PERMANENT DIPOLE FORCE
3. DIPOLE-TO-INDUCED FORCE
4. INTANTANEOUS-TO-INDUCED FORCE

以MAGNITUDE由大至細排列: 1>2>3>4

2012-05-14 11:22:56 補充:
1. 同2. 都係PERMANENT既, 即係唔會冇LALA斷左/冇左
3. 同4. 都係TEMPORARY既, 會好快斷. 3. 幾形成係由於一個POLAR MOLECULE同一個NEUTRAL MOLECULE會合, POLAR MOLECULE如水INDUCES到D CHARGES ON NEUTRAL MOLECULE, 令兩者ATTRACT EACH OTHER. 3. 相對1., 2.弱.

2012-05-14 11:23:06 補充:
4. 係由MOLECULES既電子雲(ELECTRON CLOUD)既FLUCTUATION而導致既CHARGES而引起既. 簡單D嚟講, 一個MOLECULE既ELECTRON係一個圓球體, 但佢唔會時時都噤圓, 有時會直左有時會長左, 令到一邊電子多D一邊相對地少D而形成SLIGHTLY既-VE AND +VE CHARGES. 因此個MOLECULE係暫時性POLAR而佢POLAR又會好似係3. 個CASE噤去ATTRACT其他NEUTRAL MOLECULE.

2012-05-14 11:24:28 補充:
CORRECTION: .....一個MOLECULE既ELECTRON CLOUD係.....
2012-05-13 5:19 am
Cl 電子有效地分散=3s & 3p電子層空間較大,電子密度較少->對帶正電荷物質吸引力減弱?


收錄日期: 2021-04-29 00:00:49
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120512000051KK00605

檢視 Wayback Machine 備份