Physical Chemistry

[SYWong]

I've a problem with the coordinate bond. Based on my understanding, it's the bond formed between atoms when one of them contribute electrons while the other does not. In the formation of the coordinate bond, we need lone pair electrons and also empty orbital from the other atom/molecule/ion (ligand).

I wonder, in the tetraaminine copper (II) ion (correct me if the chemical name has been wrongly spelt), [Cu(NH3)4]2+, why will the copper (II) ion form bonds with FOUR ammonia? I thought copper (II) ion has only one empty orbital, that's the 4s orbital?

Would someone please enlighten me on this?

[markwongsk]

I've a problem with the coordinate bond. Based on my understanding, it's the bond formed between atoms when one of them contribute electrons while the other does not. In the formation of the coordinate bond, we need lone pair electrons and also empty orbital from the other atom/molecule/ion (ligand).

I wonder, in the tetraaminine copper (II) ion (correct me if the chemical name has been wrongly spelt), [Cu(NH3)4]2+, why will the copper (II) ion form bonds with FOUR ammonia? I thought copper (II) ion has only one empty orbital, that's the 4s orbital?

Would someone please enlighten me on this?

This answer can be found in inorganic chemistry chapter 7: d-block elements... a brief explanation

Copper is a transition element and hence able to form coordinate (dative) bonds by accepting electron pairs from ligands. Observe that copper has 29 electrons and copper (ii) ions have 27 electrons.

The electronic configuration for copper is

3d10 4s1

while that of copper (ii) ion is

3d9

Also do note that the spelling is tetraaminecopper (ii) and the correct formula is denoted as [Cu(H20)2(NH3)4]2+

As such... the copper (ii) ion has 4 empty orbitals (namely, 4s, 4px, 4py, 4pz) to form coordinate bonds with NH3 [the water is located in 4d]

[SYWong]

Oh thanks a lot for ur help...
thanks for the corrections....^^

erm...since i havent learnt the inorganic chemistry...

mind telling me that...why copper (II) will have 4 empty orbitals instead of one? i thought the electronic configuration for copper atom only up to 4s?

it will be a great help for ur enlightenment...HEHE...:D
thank you very much...~!

[markwongsk]

no problem!

Well, actually every element has all the orbitals... only up till where are they filled with electrons differ. For copper, under normal circumstances it is filled till 4s. This does not mean it does not have 4p orbitals. It only means those orbitals are not filled with electrons. The same goes with all elements. However, normally the higher orbitals will not be filled with ligands (electron pairs) as this will cause the formed hypothetical ions to be unstable (imagine Hydrogen with 6 water molecules around it... go figure XD).

In the case of Copper (ii) and any transition element (note transition, not d-block), its high charge density provides the exception for ligand formation. Thus, it is able to use its 4p orbitals without making the ions unstable.

Some other non-transitional elements which have high charge density include Be2+ and Al3+ which causes them to form complexes too

[SYWong]

erm...there's another question here...
i thought all the d-block elements are transition elements?

i think i get wat u mean...
becoz copper tends to lose different number of electrons to form cation..
its orbitals at higher levels are easier to be coordinate bonded..
does this mean tat, copper can form coordinate bonds with different number of other atoms besides ammonia?

in conclusion, elements which can lose different number of atoms, are able to form coordinate bonds even in the higher energy orbitals which are not electron-filled initially?

thanks again for ur help!!! :D

[markwongsk]

Definition of transition element:

An element which can form a stabil ion which has partially filled d-orbitals.

As in the case of Sc, although it's a d-block element, it's ion, Sc3+ has configuration

3s2 3p6 (electrons are removed from 4s and 3d)

therefore they are no electrons in the d-orbital, violating the definition of a transition element.

For Zn, although it's a d-block element, it's ion, Zn2+ has configuration

3s2 3p6 3d10 (electrons are removed from 4s)

Therefore the d-orbitals are fully filled and thus it violates the definition of a transition element.

does this mean tat, copper can form coordinate bonds with different number of other atoms besides ammonia <--

I do not understand this question. Did you want to ask that copper can form different number of coordinate bonds? or did you mean that copper can form coordinate bonds with different types of ligands (atom is not a very good term)?

As for the first case, normally the number of coordinate bonds are fixed so as to allow copper to have a tetrahedral, square planar or octahedral shape. You just have to memorize the ligands and their formula =)

Copper can form coordinate bonds with different ligands. Other examples include aqua (H2O), chloro (Cl) etc. There's also bidentate ligands (ligands which contributes two electron pairs per molecule) eg glyoxim and polydentate ligands eg EDTA... Don't worry if you don't understand... you'll reach it soon enough =)

[anbbly]

i saw in TYT chemistry reference book:
nitrogen molecule is isoelectronic v carbon monoxide(containing 28 electrons).

based on my understanding,both N2 and CO hav 14 electrons only.
but if i count v their RAM,both of their RAM r 28.
It is a mistake on d reference book o i m wrong?

[SYWong]

Definition of transition element:

An element which can form a stabil ion which has partially filled d-orbitals.

As in the case of Sc, although it's a d-block element, it's ion, Sc3+ has configuration

3s2 3p6 (electrons are removed from 4s and 3d)

therefore they are no electrons in the d-orbital, violating the definition of a transition element.

For Zn, although it's a d-block element, it's ion, Zn2+ has configuration

3s2 3p6 3d10 (electrons are removed from 4s)

Therefore the d-orbitals are fully filled and thus it violates the definition of a transition element.

does this mean tat, copper can form coordinate bonds with different number of other atoms besides ammonia <--

I do not understand this question. Did you want to ask that copper can form different number of coordinate bonds? or did you mean that copper can form coordinate bonds with different types of ligands (atom is not a very good term)?

As for the first case, normally the number of coordinate bonds are fixed so as to allow copper to have a tetrahedral, square planar or octahedral shape. You just have to memorize the ligands and their formula =)

Copper can form coordinate bonds with different ligands. Other examples include aqua (H2O), chloro (Cl) etc. There's also bidentate ligands (ligands which contributes two electron pairs per molecule) eg glyoxim and polydentate ligands eg EDTA... Don't worry if you don't understand... you'll reach it soon enough =)

does this mean tat, copper can form coordinate bonds with different number of other atoms besides ammonia <--

LOLz...i agree tat my "atom" is not a good term here...haha..should be particles..i think?zzz

i've gt the answer from ur reply...^^ thanks a lot!:nod

nice to meet you here~~~~

[ChristopherCWL]

Hey , i have a question here...may i know why is the graph for PV against P is equal to constant de??? can some1 answer it to me?? pls

[Boyz_Zoo]

Hey , i have a question here...may i know why is the graph for PV against P is equal to constant de??? can some1 answer it to me?? pls
cause PV = k, where k is a constant. Therefore, under the standard temperature, the product of pressure and volume will be the same regarless tothe variation in quantity for P and V.

That is why, the graph is constant.

[markwongsk]

@<hidden>: Yea I think the book got it wrong =)

@<hidden>: Boyle's Law states that pressure is inversely proportional to Volume, so PV = k as what Boyz wrote.

so if you're plotting PV against P, you're plotting a constant k for all values of p, hence a straight line