[timchai]

Because its boiling point is much lower, it follows that beryllium chloride can't contain ions - it must be covalent quote from http://www.chemguide.co.uk/inorganic/group2/beryllium.html#top.can u explain , i want to ask why Be has lower b.p . and mp. than MG
can we say it has  high concalent character , so wan der Waals' force ...

[Vidya]

You are absolutely correct....

Beryllium differs from the rest of the group because small size,high electronegativity.Be-Cl bond has less difference in electronegativity which favours covalent character.
Covalent compounds have lower m.pts or b.pts because of weak IMF

[ARGOS++]

Dear vidya kaushik;

I can't agree with you, when you talk about the "exceptional low" Mp. and Bp. of Beryllium.

Beryllium has except the half part of "Rare Earth" and "Transition Metals", the third highest Mp. and the second highest Bp of all Elements.
It is known as an exception because it has the exceptional highest Mp. and Bp. of "all" Light Metals and that's exactly why it is so much preferred for tech. constructions (also some other special properties!).
But I agree that Beryllium has an exceptional small radius and a very high covalent character and a less metallic character.

Maybe you should also visit once:
     http://www.chemicalelements.com/show/meltingpoint.html
     http://www.chemicalelements.com/show/boilingpoint.html
     (- and Wiki.)

Good Luck!
                    ARGOS⁺⁺

[Vidya]

Hello
Please take care
I didn't write exceptionally low any where.