why are some bonds not pure covalent or ionic?

Question

For instance quartz-Si02 is considered to be essentially "purely" covalent but with a ionic behavour as well. . I do understand that bonds between the same non metal elements are pure covalent such as Cl-Cl and O-O. is the bond NaCl purely ionic? I am not sure.
Any help would be appreciated.

Answer 1

In general chemistry - normally what is said is that your diatomics (H2, N2, O2 and so on) are pure covalent - they share their electrons perfectly. And generally speaking, it is taught that group 1A cations and 7A anions make a "perfect" ionic situation.

It has been discovered, through examining the electrons and their location, that even those purely ionic species "share" the electrons slightly between them!!

Everyone else on the periodic table, because their electron affinity values/ionization energy values become closer and closer - neither species wants to completely lose nor completely gain the electrons - so they end up somewhere in the middle (examine Linus Pauling's electronegativity scale. It's is NOT a perfect scale, but it does work well. If you take the two atoms in the bond, and subtract the electronegativity values if you are > 1.7 you are said to be ionic, or < 0.4 you are said to be non-polar covalent and everything inbetween is polar covalent (which is the inbetween).

But just so you know there isn't even a pupre non-polar covalent if you want to get nitpicky because O2, N2, F2, etc efven though they are naturally occurring shifts in electron density which gives rise to something called London/dispersion forces - these forces are sooooo strong that it makes I2 a solid and Br2 a liquid!!)

It's called the bonding continuum for a reason!

Answer 2

NaCl is only 63% ionic, which is pretty shocking to those who have been taught that it is totally ionic!
Virtually all bonds (except those between identical atoms such as in Cl2 or O2) are polar to some extent, and this is caused by a difference in electronegativity, or electron-pulling power. There is a whole spectrum of types of bond, with covalent and ionic being the two extremes.

Answer 3

there are some atoms dat share electrons inorder to form a covalent bond, but they do not form a purely covalent bond eg:- HCl, HBr HI
this is bcoz of electronegativity differences between the the hydrogen atom and the halogen atoms
hydrogen is less electronegative than the halogen atoms so the halogen atoms being much more electronegative tend to pull the shared electrons MUCH MORE towards themselves
therefore the bond formed in HCl HBr HI is not purely covalent...and such a bond is called a "polar" covalent bond
for more info..chek da websyt www.chemguide.co.uk

and reagrdin NaCl...ive read in books sayin dat NaCl is ionic but neva read so far whether it is purely ionic
newys u can chek the websyt ive givn above..
there is complete info on ur ques. in this websyt