1. A Case Study on Covalent Bonding Done By Ng Jia Neng (27) 2O2

2. Agenda Introduction Research Explanation Conclusion

3. Covalent Bond A covalent bond is formed by two atoms sharing a pair of electrons.

4. Covalent Bond The atoms are held together because the electron pair is attracted by both of the nuclei.

5. An example of covalent bonding HH

6. Rules and regulations Covalent bonds are formed between atoms of non-metals.

7. Exceptions Aluminium chloride & Beryllium chloride are covalent compounds

8. Exceptions Both compounds should be ionic in nature.

9. Aluminium + Chlorine Video of the reaction http://www.youtube.com/watch?v=F4IC_B 9i4Sghttp://www.youtube.com/watch?v=F4IC_B 9i4Sg

11. Simpler substances 2 Sections Aluminium Chloride Aluminium Chloride Beryllium chloride Let’s talk about Aluminium Chloride first…

12. 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. )

13. Reasons behind the mystery… This is due to polarisation. Cations are very polarising, while anions are very polarisable.

14. 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-.

15. So what? This causes the electrons cloud of the Anion, Cl- to be distorted and be attracted to the Cation, Al3+.

16. 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.

17. Illustration

18. Tracing back… 2 Sections Aluminium Chloride Aluminium Chloride Beryllium chloride Back to Beryllium chloride…

19. Same concept… Beryllium chloride is also an ionic bond with a higher degree of covalency.

20. 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-.

21. The same goes…… This causes the electrons cloud of the Anion, Cl- to be distorted and be attracted to the Cation, Be2+.

22. 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.

23. Illustration

24. 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.

25. Credits Yahoo answers  http://answers.yahoo.com/question/index?qid=200 90905074529AAMbyCs http://answers.yahoo.com/question/index?qid=200 90905074529AAMbyCs  http://answers.yahoo.com/question/index?qid=200 80311053839AAgwFA3 http://answers.yahoo.com/question/index?qid=200 80311053839AAgwFA3 Answers.com Chemguide.co.uk  http://www6.grafton.k12.wi.us/ghs/teacher/mstaud e/covalentbonds.htm http://www6.grafton.k12.wi.us/ghs/teacher/mstaud e/covalentbonds.htm

26. Thank you And have a nice day