Why reducing nature of hydrides increases down a group?

[Raghav Gupta]

But for oxides reducing nature decreases down a group.
We say non metallic oxides are acidic but for hydrides it is opposite,
What's the appropriate reason?

 

[proton007007]

Down a group , the metal electropositivity increases and so negative charge comes up on the hydride more easily

 

[Raghav Gupta]

Down a group , the metal electropositivity increases and so negative charge comes up on the hydride more easily

Okay but then why

For oxides reducing nature decreases down a group.

 

[AdityaDev]

Are you learning p-block?
Anyway,the bond dissociation energy for hydrides decreases down a group. So reducing nature increases

 

[Raghav Gupta]

Are you learning p-block?

Yes you are right.

Anyway,the bond dissociation energy for hydrides decreases down a group. So reducing nature increases

okay, the only question that remains is that why,

For oxides reducing nature decreases down a group.

?

 

[Suraj M]

Going down the group, wouldn't the bond between the atom and oxygen get weaker, so the atom would furnish Oxygen easily which would would actually increase oxidizing power.
But then again, contradicting the above statement, going down the group decreases the number of O atoms(inert pair e.) on the Non metal, which would again decrease the oxidizing power of the oxide.
And also i remember reading somewhere(NCERT) that larger the atom, more ability to stabilize the oxide ions(read it under s-block).That would mean it would decrease the oxidizing power.
I;m a bit confused on how to consider all these factors,

 

[proton007007]

But for oxides reducing nature decreases down a group.
We say non metallic oxides are acidic but for hydrides it is opposite,
What's the appropriate reason?

Please provide an example where you have the doubt

 

[Suraj M]

Please provide an example where you have the doubt

Proton, could you telm me if it is true that the reducing power of oxides decreases down the group!

 

[proton007007]

Proton, could you telm me if it is true that the reducing power of oxides decreases down the group!

As I said , give an exmple of the compound . Metallic and non-metallic oxides have different variations .

 

[Suraj M]

He said p block. right?

 

[proton007007]

He said p block. right?

If I am not mistaken , p-block is not a compound !
CO is the most common OXIDE reducing agent . Do you expect Sodium oxide to behave as a good reducing agent ?

 

[Suraj M]

Oh ok sorry.

 

[Raghav Gupta]

As I said , give an exmple of the compound . Metallic and non-metallic oxides have different variations .

I would give example, but first tell me that does increasing reducing strength means more basicity?

 

[Raghav Gupta]

I think this all acidity, oxidizing strength is related.
But not able to find the real difference between Hydrides and oxides.
We say non metallic oxides like CO₂ are acidic but MgO are basic. Why that is the case?
I saw some sites but they give the reason of dissolving in water to form alkali for basic oxides. That's experimental and not a logic by theory.
This was taught in our school but theoretical logic was not given.
We say down the group basic nature of oxides increase for any group not only taking p block but all groups.
For hydrides that is opposite, why ?
I expect NaO to be a oxidizing agent.

 

[Jack2]

basicity of hydrides decreases down the group in group 15 and 16 . Missed out the ones

 

[Raghav Gupta]

basicity of hydrides decreases down the group in group 5 and 6

You mean the d block?

 

[Jack2]

I edited the post

 

[Raghav Gupta]

But why only 15- 16?

 

[Jack2]

But why only 15- 16?

Proton007007 asked for a compound above (maybe) because all groups don't have hydrides with lone pair .
I said 15 and 16 as they have lone pairs to donate and qualify as Lewis Base .

 

[Raghav Gupta]

Proton007007 asked for a compound above (maybe) because all groups don't have hydrides with lone pair .
I said 15 and 16 as they have lone pairs to donate and qualify as Lewis Base .

So what about group 17 of halogens. They also have lone pair.
Acidity for hydrides of halogens increases down the group. Like HI>HBr>HCl>HF
Here also basicity is decreasing down the group.

 

[Raghav Gupta]

Going down the group, wouldn't the bond between the atom and oxygen get weaker, so the atom would furnish Oxygen easily which would would actually increase oxidizing power.
But then again, contradicting the above statement, going down the group decreases the number of O atoms(inert pair e.) on the Non metal, which would again decrease the oxidizing power of the oxide.
And also i remember reading somewhere(NCERT) that larger the atom, more ability to stabilize the oxide ions(read it under s-block).That would mean it would decrease the oxidizing power.
I;m a bit confused on how to consider all these factors,

Not understanding the third part.
How larger the atom stabilizes oxide ions? There is inert pair effect right?

 

[Suraj M]

There is inert pair effect right?

no no not inert pair effect,, do you remember why only heavier metals can form superoxides, i just tried to apply the same concept!

 

[Raghav Gupta]

no no not inert pair effect,, do you remember why only heavier metals can form superoxides, i just tried to apply the same concept!

Okay like KO₂.
Why not p block elements form super oxides?

 

[Jack2]

So what about group 17 of halogens. They also have lone pair.
Acidity for hydrides of halogens increases down the group. Like HI>HBr>HCl>HF
Here also basicity is decreasing down the group.

I would strongly advise you to read this up . It will give you an idea for your halogen statement .

 

[Raghav Gupta]

I would strongly advise you to read this up . It will give you an idea for your halogen statement .

I was reading that but there the wikipedian has written citation needed where he/she is saying following compounds are hydrogen and not hydrides, means he/she can be lying.

Basically what I meant in this thread is hydrogen bonding to elements whether it would be a hydride or hydrogen that's all nomenclature but a hydrogen is hydrogen.
Now one can also argue with oxides, there are peroxides, superoxides. But what really matter is linkage of element with oxygen.

Now in a nutshell if we consider 17 group does down the group oxides of it show basic nature?

 

[AdityaDev]

Group 17 oxides are unstable.lets Start with ClO2... It has odd number of electrons and is highly reactive and it is acidic.
Next,Cl2O6... It is also reactive and acidic.
Cl2O7... Moderately stable.
Cl2O... Again acidic,which is evident from its reaction with NaOH to give sodium hypochlorite and water.
O2F2... Violent oxidizing agent. Also used as flourinating agent.
OF2... Not an acid anhydride.reacts vigourously with metals and used as rocket fuel.

In a nutshell,all these oxides are explosive and unstable. Such compounds are not important for JEE and NCERT. you have to know that they are oxidizing.

 

[AdityaDev]

Not understanding the third part.
How larger the atom stabilizes oxide ions? There is inert pair effect right?

Inert pair effect favours oxidation lower oxidation state and this has good effect only on Bi. I don't think you should apply it here. Also the bond dissociation energies of E-O where E is non metal keeps decreasing as one goes down a group.

 

[AdityaDev]

Lower oxides of nitrogen are neutral and higher ones are acidic.

 

[Raghav Gupta]

Lower oxides of nitrogen are neutral and higher ones are acidic.

Can you give the reason for that statement?
There are some questions being skipped.
Can we say taking whole periodic table except lanthanides, actinides and recently found elements that hydrides or hydrogen bonded with element down the group reducing nature increases, even for s block, p block and d block?
Down the group metallic nature increases
So how down the group element oxides show more basic nature but for hydrides that is opposite?

 

[AdityaDev]

Solution for your problem: refer JD Lee. (The original version. Not the iitjee edition)

 

[AdityaDev]

After reading it, you possibly won't come back to the thread.

 

[Raghav Gupta]

After reading it, you possibly won't come back to the thread.

Alas. I don't have that.
Can you tell only why metallic oxides are basic in nature.

 

[AdityaDev]

You can get the ebooks online at cheap rates.
metallic oxides are basic in nature because they react with water to form metal hydroxides which are basic in nature.

 

[Raghav Gupta]

metallic oxides are basic in nature because they react with water to form metal hydroxides which are basic in nature.

So why metallic hydrides are not basic?

 

[AdityaDev]

I have never read about basic nature of hydrides. They are known to be reducing agents. Alkali metal hydrides react with water liberating hydrogen gas and a hydroxide. Also such hudrides are called salt-like hydrides not acidic or basic hydrides. But non metal hydrides are basic like NH3.

 

[Raghav Gupta]

I have never read about basic nature of hydrides. They are known to be reducing agents. Alkali metal hydrides react with water liberating hydrogen gas and a hydroxide. Also such hudrides are called salt-like hydrides not acidic or basic hydrides. But non metal hydrides are basic like NH3.

But when comparing acidity of NH3,PH3,AsH3,SbH3 we say that Down the group acidity increases which is analogue to up the group basicity increases?

 

[AdityaDev]

That is because of low electron density at central atom. As size increases, the electron density around central metal atom decreases hence basicity decreases.

 

[Raghav Gupta]

That is because of low electron density at central atom. As size increases, the electron density around central metal atom decreases hence basicity decreases.

So why that statement is wrong in case of oxides of that group?

 

[Raghav Gupta]

I would strongly advise you to read this up . It will give you an idea for your halogen statement .

In continuation with post #25 why then group 16? Wiki is showing that they are not hydrides but like hydrogen selenide, hydrogen oxide etc.

 

[Jack2]

In continuation with post #25 why then group 16? Wiki is showing that they are not hydrides but like hydrogen selenide, hydrogen oxide etc.

Hydride mean a hydrogen atom with a negative charge .
In all halogens , hydrogen has +1 charge . They are called acids , not hydrides .
In group 16 , the lower elements are metallic ( having EN less than 2.1 ) so their compounds can be called hydrides . So I made a generalized statement .
But surely halogen groups don't form hydrides .

 

[Raghav Gupta]

Why the generalized statement , when only in that group Polonium is a metal? It should be called a exception from 16 group.
and what about this?

I was reading that but there the wikipedian has written citation needed where he/she is saying following compounds are hydrogen and not hydrides, means he/she can be lying.

Basically what I meant in this thread is hydrogen bonding to elements whether it would be a hydride or hydrogen that's all nomenclature but a hydrogen is hydrogen.
Now one can also argue with oxides, there are peroxides, superoxides. But what really matter is linkage of element with oxygen.

 

[Borek]

To all - please keep your posts on topic and if you have new questions, start a new thread.

 

[Raghav Gupta]

To all - please keep your posts on topic and if you have new questions, start a new thread.

I few days ago started a new thread but got only one reply and none then.
Even if you have said I don't know it would have been fine( I know elders hesitate to say this sometimes but then also basic etiquettes are required).

Anyway I agree with you that for new questions new thread must be started and by the way excluding 2 threads you have helped me a lot in chemistry.
But any comment or reply for first para?