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Covalent Bond
The atoms are held together because the
electron pair is attracted by both of the nuclei.
Aluminium + Chlorine
Video of the reaction• http://www.youtube.com/watch?v=F4IC_B
9i4Sg
Simpler substances
2 Sections
Aluminium Chloride
Beryllium chloride
Let’s talk about Aluminium Chloride first…
Reasons behind the mystery…
Even though the bond is between a metal and non metal, it is
highly covalent. ( In other words, it is an
ionic bond with a higher degree of
covalency. )
Reasons behind the mystery…
This is due to polarisation.
Cations are very polarising, while anions
are very polarisable.
Explanation
The Cation, Al3+, has a very high polarising power due to its high positive charge and
small size. It can polarise the electron cloud of the Anion,
Cl-.
So what?
This causes the electrons cloud of the Anion, Cl- to be distorted and be attracted to the Cation, Al3+.
Resulted in……
Other than a transfer of electrons from aluminium to chlorine, the electrons are shared between the atoms and hence it has a higher degree of covalency.
In this case ~
The Cation, Be2+, has a high polarising power due to its high positive charge and small size. It can polarise the electron cloud of the Anion, Cl-.
The same goes……
This causes the electrons cloud of the Anion, Cl- to be distorted and be attracted to the Cation, Be2+.
Outcome…
Other than a transfer of electrons from Beryllium to chlorine, the electrons are shared between the atoms and hence it has a higher degree of covalency.
In a nutshell
• Aluminium chloride and Beryllium chloride are covalent bonds because of polarisation. It occurs between a small cation with high charge density and a larger anion.
Credits
• Yahoo answers http://
answers.yahoo.com/question/index?qid=20090905074529AAMbyCs
http://answers.yahoo.com/question/index?qid=20080311053839AAgwFA3
• Answers.com• Chemguide.co.uk http://www6.grafton.k12.wi.us/ghs/teacher/mstaud
e/covalentbonds.htm