hypervalent.....

ans should be (B) and (C)...

ya in SO₄^2- sulfur forms double bonds with oxygen.... not dative bonds..

infact all the options are hypervalent....

Well if you see, all the options are hypervalent, so I think they all are hypervalent compounds.

@ Vivek, if I am not ignorant, arihant mein hypervalency ke bare mein kuchh nahi hai

Hahaha!! @Khyati I think ClO₄^- is also among the answer.
Sorry But I don;t have Arihant's any Chemistry book!

@ Vivek I think they dont follow the conditions that I mentioned in #5 post, so they are not considered hypervalent.

Anyways I'll try to search better reasons

@ Euclid SO₄^-, S doesnt form dative with O here, its structure was given wrong in arihant so I made a mistake. Sorry.

@ Vivek, don't know yaar. [3]

I saw ClO₄^- structure, it too contains more than octet of electrons.

Let's wait some others to reply

the answer given is ABCD

Answer to your question is the option (B) PO₄^-3

http://en.wikipedia.org/wiki/Hypervalent_molecule(see for more information)

The hydrogen bond is one of the best examples of a hypervalent bond

Stable compounds of the main group elements in the third row of the periodic table, such as

silicon, phosphorus, and sulfur, that have more than eight valence shell electrons, for

example, PF5 and SF4.

Group 1, 2, and 13–18 compounds which contain a number (N) of formally assignable

electrons of more than eight (octet) in a valence shell directly associated with the central

atom (X) in direct bonding with a number of ligands (L). The designation N-X-L is conveniently

used to describe hypervalent molecules.

In the periodic table, compounds of main group elements in the second row (such as

carbon, nitrogen, and oxygen) have eight valence electrons. As such, the fundamental

shapes of their atoms are linear (such as acetylene, sp orbital), triangular, (such as

ethylene, sp2 orbital), and tetrahedral (such as methane, sp3 orbital). In contrast, main

group elements in the third row of the periodic table (such as silicon, phosphorus, and

sulfur) may contain more than eight electrons in a valence shell. These are called

hypervalent compounds. Fundamental shapes of 10-X-5 molecules (including 10-X-4

molecules bearing a pair of unshared electrons) are trigonal bipyramid (TBP) or square

pyramid (SP), and those of 12-X-6 (including 12-X-5 bearing a pair of unshared electrons)

are octahedral. Hence, there is an apparent similarity in shape between hypervalent

compounds and organotransition metal compounds.

@ Qwerty you are correct, you just missed one thing,i.e, they are stable also even though

they have more than octet of electrons.