A Case Study on Covalent Bonding

Done By

Ng Jia Neng (27)

2O2

Agenda

• Introduction• Research• Explanation• Conclusion

Covalent Bond

A covalent bond is formed by two atoms

sharing a pair of electrons.

Covalent Bond

The atoms are held together because the

electron pair is attracted by both of the nuclei.

An example of covalent bonding

• H • H

Rules and regulations

Covalent bonds are formed between atoms

of non-metals.

Exceptions

Aluminium chloride & Beryllium chloride

are covalent compounds

Exceptions

Both compounds should be ionic in nature.

Aluminium + Chlorine

Video of the reaction• http://www.youtube.com/watch?v=F4IC_B

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Why ???

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.

Illustration

Tracing back…

2 Sections

Aluminium Chloride

Beryllium chloride

Back to Beryllium chloride…

Same concept…

Beryllium chloride is also an ionic bond

with 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.

Illustration

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

Thank you

And have a nice day