[miracle]

hi all,

I want to ask what is the relation between "electronegativity(EN)", "polarizability", "polarizable" ? are the applications of these terms restrict solely to covalent bonds or solely to ionic bond? or is it just free for us to apply them to whatever kind of bond?

besides, in the comparison between CBr4 and CCl4's boiling point, why don't we refer to the difference in EN but say that Br is more polarizable so it has a stonger intermolecular force and higher b.p.?

in case of comparing HBr, HCl's boiling point, what should we use to explain? EN or "more polarizable" or something else?

thanks for your help. exam ahead.

[abdulgaballa]

Hey
 
The answer to your first question is that the second two determine to what extent a compound is covalent if ionic; the term polarising refers to the ability of a cation to distort the electrons around an anion (charge density) in order to make the compound  more covalent. The first term, however, is more of a single element characteristic, its like saying john is more attractive to girls than Ben, so Flourine is more electronegative than Chlorine.

In respond to your second question, you must understand that when chemists talk of elctronegativity they are mainly considering the affect of the difference in EN in a compound in order to observe the limit to which a covalent compound is polar. In order to predict other properties such as solubility and reactivity. When talking about the melting points of Compounds, such as HCl and HBr, you only consider the INTERMOLECULAR forces between the molecules in a compound, In this case, Van de Waal's forces. When it comes to VdW's forces, it is the size of the molecule that makes a difference, as there are more electrons to form instantaneous dipoles.

Hope that makes thins a bit clearer!
 

 

[IITian]

In addition, Electronegativity, is a property that describes the capability of an atom (or, more rarely, a functional group) to attract electrons towards itself. Pioneered by Linus Pauling in 1932 as a development of valence bond theory, it has been shown to correlate with a number of other chemical properties.

Polarizability is the relative tendency of a charge distribution, like the electron cloud of an atom or molecule, to be distorted from its normal shape by an external electric field, which may be caused by the presence of a nearby ion or dipole

ref: wiki

[dipnosti]

helpp..ı m realy confused about polarity what is the diffrence polarity of a molecule and bon polarity how do we decide on largest polarity..it can be so simble but ı couldnt understand why hcl has the largest polarity(among Br2,Ne,HCl,HBr and N2) pleas help me to overcome because ı have an examination on saturday morning

[Alpha-Omega]

The reason that HCl has the largest polarity is beacuse the H and Cl are most different in nature.

Br₂ =  2 of the same species bound together least polar

Ne = has 8 e in the electron shell   does not bond...has full shell-NOBEL GAS STRUCTURE atom with closed shell.

HCl:  note here that H is highly electropositive and Cl a halogen is highly electronegative-this is an extremely polar molecule compared to the others in this series...small + on that H and large - on that Cl....and the H is far smaller than that Cl...large e- cloude about that Cl and has an effect on the electronegativity and polarity.

HBr:  also polar less than HCl...Br is less electronegative than Cl in the halogen series in order of electronegativitiy:  F>Cl>Br>...

N2  = molecular non-polar equal e- on both atoms....clouds same on both eds...symmetry is preserved...highly symmetrical non-polar

Electronegativity increase across a period in the Periodic Table and decreases from top to bottom in a group:  general rule...some variations...

http://en.wikipedia.org/wiki/Electronegativity

[dipnosti]

thanks a lot..I really got the point now ı m happyy

[Alpha-Omega]

This is a very nice site for learning the PERIODIC TRENDS:  http://dl.clackamas.cc.or.us/ch104-06/periodic.htm

Glad to *delete me*!!!