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COVALENT BOND VS IONIC BOND
You have seen how elements are similar to us and as you know them closely you will find some more similarities to our behaviour. You must have experienced the law of attraction in your life. We tend to get attracted towards someone opposite to us. Elements too experience this law of attraction. They are likely to bond with the element quite opposite to their characteristics. You can see, this phenomenon working on the elements placed on two opposite sides of the periodic table (group 1 and group 17).
Group 1 and group 17 have opposite qualities. Group 1 has least Ionization enthalpy (easy to remove electron from valence shell) while group 17 has least Electron gain enthalpy (easy to add electron to valence shell ). Group 1 is least electronegative and group 17 is the most electronegative. That’s why group 1 elements easily donate one of their valence electron to group 17 elements. Thus group 1 elements form M+^ ion and
group 17 elements form X-^ ion. And these two oppositely charged ions attract each other and make ionic bond. The force they experience is called as electrostatic attraction. Group 2 and group 17 also make ionic bonds for the same reasons.
Now, I want you think of your friends. For a moment, go in the past and think, why did you make him/her your friend? You must have found them quite similar to you. People with common interest like to unite together. Elements also make bonds with elements which have similar qualities.
Group 13, 14, 15, 16 and 17 all are p block elements. They all have a few similarities. They have almost similar values of IE and EGE. They are all on the same ground; no one is capable of donating/ accepting electrons, that’s why they share electrons between them and form covalent bonds.
Now this may contradict your logic, you might have thought that the ionic bonds must be tougher and stronger than covalent bonds. Ionic bond is undoubtedly weaker than covalent bond but electrostatic attraction between ions and the strategy of ionic molecules to arrange them in a network (lattice) give extraordinary strength to the ionic compounds. “Unity in Strength”, this quote is also true in the world of atoms and it is the reason behind the strength of NaCl. NaCl molecules are bound together by electrostatic force to form a cubic structure and a number of such cubes form a network structure (where each Na+ issurrounded by 6 Cl- and each Cl- is surrounded by 6 Na+) which gives strength to the common salt. The electrostatic force is the strongest force working between ions and molecules of ionic substances which gives them extraordinary strength in spite of their weaker bond.
In covalent compounds, forces operating between molecules are not as stronger as electrostatic force. But it doesn’t mean that all covalent compounds are liquids or gases, some are solids too.
At this point, when you have learnt about bonds and their nature, you would like to try different combinations of elements. And you must be curious to know whether it exists or not and what would be the name of that compound? In the next post we will learn
how to make a compound? How to work out the formula of the compound and also how to name it?
Source : http://chemistrynotmystery.blogspot.in/2014/07/covalent-bond-vs-ionic- bond.html?view=sidebar
