Beginners --> Chemical Bonding

5. Discuss the Re-Re bonding in molecule of [Re2X8]2- ?

Oh. Thanks. But I couldn't understand there. It's much more deeper there mentioning spectra of those. I need only structure.

For structure see http://en.wikipedia.org/wiki/Quadruple_bond

It is made up of 2 approximately square planar ReX₄ units linked by a Re-----Re bond of length 2.24angstrom.

The metal bond is very short and is interpreted as a quadruple bond. If Re-----Re bond points along the z axis the square planar units uses s,p_x, p_y and d_x2-y2 orbital for σ bonding to the X atoms. A sigma bond between the two Re atoms will have the contribution from the p_z and d_z2 orbitals which lie along the axis. With the eclipsed conformations the d_xz and d_yz orbitals on the two Re atoms overlap sideways forming two pie bonds. Finally the d_xy orbitals which lie in the two ReX₄ planes overlap with each other, giving a δ bond

Why does it dissociates in [PCl4]+ and [PCl6]-. What is the cause of it's high reactivity

Why doesn't it dissociate like this : [PCl3]2+ and [PCl7]2-. ANy reason.?

One reason I can think for its high reactivity is that its hypervalency (PCl₅₎ is hypervalent).

why doesn't is dissociate the way you want is, I think PCl₃⁺² has less than a octet so its unstable and hence combine with one more Cl^- to form [PCl₄]⁺ and the [PCl₇]^2- will be to unstable to exist because of the repulsion, after all phosphorus is not big atom, its a small one ,it can't accommodate 7 chlorine atom which are of course bigger than it, so because of the repulsion it end up forming [PCl₆]^-.

How the molecules form and what kinda shape they have that's solely depends on its stability, if its stable it cant exist, if it isn't, then it cannot.

Hope this clear your this one doubt and others one too that you have been getting about this one.

'Can 2S and 2Py combine?'

Well an s orbital combine with a p orbital provided that the lobes of the p orbital are pointing along the axis joining the nuclei.

And they do combine in the formation of lithium carbide and beryllium carbide.

LiC≡CLi (structural formula)

What you said explains that there should be 5 Maximum orbitals in d subshell. But why it should be dz2 only and not the others I mentioned.

elliptical orbits can take up only certain orientations with respect to the external field rather than precessing freely.

Forgot to read this?

Electronegativity Scale more accurate or better than Allred and Rochow's?

They all are equal and are related to each other in one or other way. So I think all of them are better and accurate in their own way.

Discuss Structure of I8-

Din't got any information about this. Is this molecule your brain growth?????

Can 1s2 and 1s2 AOs Combine

The energy in the bonding molecular orbital is lower than that of the atomic orbital by an amount Δ. This is known as the stabilization energy. The saving of 2Δ energy corresponds to the bond energy,i.e, formation of bonds. The bond is formed when there is a saving of energy when the orbitals combine to form bonds. It is only the system is stabilized in this way and the bond is formed.

Now consider your case which is like the He atoms combining (its hypothetical). the 1s orbitals on each He contains 2 electrons making a total of 4 electrons to put into MOs. 2 of the electrons occupy bonding MO and 2 occupy antibonding MO. The stabilization energy 2Δ derived from filling the bonding MO is offset by the 2Δ destabilization energy from the antibonding MO. Since overall there is no energy saving, He₂ does not exist and this situation corresponds to non bonding. Means 1s² and 1s² cannot combine.

Why isn't there any dy2-z2 or d z2-x2 orbital ?

Zeeman showed that if atoms were placed in a strong magnetic field additional lines ( along with spectral lines) appeared on the spectrum. This is because elliptical orbits can take up only certain orientations with respect to the external field rather than precessing freely. Each of these orientations is associated with a magnetic quantum number (m) which can have values of -l, 0,..............+l (l is the azimuthal quantum number)

Thus a single line in the normal spectrum will appear as (2l + 1) lines and this is the reason for existence of certain orbitals and their location is space is determined by the research done by the scientist ( I mean whether they exist in xy plane and ...........)

3. Compare the Shapes and geometry of Nitrite and Nitrile -->

Nitrile:- It has a linear structure

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

Nitrite:- Its a V- shaped ion, this is based on a plane triangular structure with N at the centre, 2 corners occupied by O atoms and the third corner occupied by a lone pair. The N atom is roughly sp² hybridized.

One from other Topic :

1. Why isn't there any d_y²-z² or d _z²-x² orbital ?

Cause we have d_xy , d_yz, d_zx , d_x2-y2!

2. Probably Only Xe and one other [Kr] among the Noble/Inert gases form the compounds. Why is it so if they have a complete and stable octet and If they do why other Inert gases don't?

3. Electronegativity Scale more accurate or better than Allred and Rochow's?

4. Can 1s² and 1s² AOs Combine. If yes then By MOT, We have 2 AOs combine to form two MOs. As for example say 1s2 of one atom and 1s2 of other combine to form \sigma 1s^{2} and \sigma^{*} 1s^{2} each having 2 electrons distribution.

Now Bonding Orbitals are formed by same phase Overlapping while Anti Bonding are formed by Out phase overlapping. How is this possible simultaneously as we have a pair of same phase electrons.

else, that will clear my doubt.

What is the cause for 4.)
Why does it dissociates in [PCl4]+ and [PCl6]-. What is the cause of it's high reactivity

That's experimental reason and the conclusion is due to research I think.

4. LiCl and NaCl -- Which would ionise more in water ?

NaCl will ionise more in water.

2. Probably Only Xe and one other [Kr] among the Noble/Inert gases form the compounds. Why is it so if they have a complete and stable octet and If they do why other Inert gases don't?

The noble gases have full valence electron shells. Valence electrons are the outermost electrons of an atom and are normally the only electrons that participate in chemical bonding. Atoms with full valence electron shells are extremely stable and therefore do not tend to form chemical bonds and have little tendency to gain or lose electrons. However, heavier noble gases such as radon are held less firmly together by electromagnetic force than lighter noble gases such as helium, making it easier to remove outer electrons from heavy noble gases and thus to form compounds

The reactivity follows the order Ne < He < Ar < Kr < Xe < Rn.
In theory, radon is more reactive than xenon, and therefore should form chemical bonds more easily than xenon does. However, due to the high radioactivity and short half-life of radon isotopes, only a few fluorides and oxides of radon have been formed in practice though xenon has many compounds in comparison to radon.

Krypton is less reactive than xenon, but several compounds have been reported with krypton in the oxidation state of +2. Krypton difluoride is the most notable and easily characterized. Compounds in which krypton forms a single bond to nitrogen and oxygen have also been characterized, but are only stable below −60 °C (−76 °F) and −90 °C (−130 °F) respectively).
Krypton atoms chemically bound to other nonmetals (hydrogen, chlorine, carbon) as well as some late transition metals (copper, silver, gold) have also been observed, but only either at low temperatures in noble gas matrices, or in supersonic noble gas jets. Similar conditions were used to obtain the first few compounds of argon in 2000, such as argon fluorohydride (HArF), and some bound to the late transition metals copper, silver, and gold. As of 2007, no stable neutral molecules involving covalently bound helium or neon are known.
The noble gases—including helium—can form stable molecular ions in the gas phase. The simplest is the helium hydride molecular ion, HeH+, discovered in 1925. Because it is composed of the two most abundant elements in the universe, hydrogen and helium, it is believed to occur naturally in the interstellar medium, although it has not been detected yet. In addition to these ions, there are many known neutral excimers of the noble gases. These are compounds such as ArF and KrF that are stable only when in an excited electronic state; some of them find application in excimer lasers.
In addition to the compounds where a noble gas atom is involved in a covalent bond, noble gases also form non-covalent compounds. The clathrates, first described in 1949, consist of a noble gas atom trapped within cavities of crystal lattices of certain organic and inorganic substances. The essential condition for their formation is that the guest (noble gas) atoms must be of appropriate size to fit in the cavities of the host crystal lattice. For instance, argon, krypton, and xenon form clathrates with hydroquinone, but helium and neon do not because they are too small or insufficiently polarizable to be retained. Neon, argon, krypton, and xenon also form clathrate hydrates, where the noble gas is trapped in ice

For more info see http://en.wikipedia.org/wiki/Noble_gas

7. Is there any difference between sp³d and dsp³ hybridization and Where is it and WHY?

Yeah, there is. sp³d is a outer orbital compound(since it uses the outer d orbitals) whereas dsp³ is a inner orbital compound(it uses the inner ones). I read this while doing coordination compounds. Well, this is because of the strength of the ligands that donates their electron pair to the atoms to form compunpds. strong ligands form the inner complexes whereas weak ones form the outer complexes.

Yes. Please answer the Next ones.

1) As the electronegativity of the central atom increases, it attracts the bonded pair of electrons closer to it.. This increases the electron density of the cloud around the atom and hence repulsion increases.. This causes an increase in the bond angle.