Drago's Rule | Chemical Bonding | Inorganic Chemistry for Jee Advance, AIIMS, NEET and BITSAT
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- เผยแพร่เมื่อ 13 ต.ค. 2024
- Drago’s rule is an empirical rule and is used to explain the bond angles of hydrides of group 15 and 16 of or below 3rd period. So essentially it is only applicable for PH3, AsH3,SbH3 and H2S, H2Se, H2Te.
According to drago,s rule when the following conditions are satisfied, then the energy difference between the participating atomic orbitals will be very high and thus no mixing of orbitals or hybridization takes place.
1. Atleast one lone pair must be present on the central atom.
2. The central atom must be of or below 3rd period.
3. The electronegativity of the surrounding atom must be less than equal to 2.5.
No hybridisation means bonding will take place through pure atomic p orbitals in PH3 and thus bond angle will be approximately 90.
Explaination:-
For any atomic system with more than one electron, quantum chemistry predicts the energies of the s and p subshells of a shell to differ - while for hydrogen-like systems (one-electron systems) all subshells of a given shell have the same energy. The s subshell of a certain shell in multi-electron systems has a lower energy than the p subshell which in turn has a (far) lower energy than the d subshell and so on and so forth. Since s subshell is determined to be more stable by this method, it is not surprising that the first two electrons of a given shell are added to said s subshell; the next six electrons are added to p subshells whereafter a new shell is used.
This immediately explains that it is most stable for any atom to treat the s electrons of its valence shell as ‘extended core electrons’; i.e. we can predict any configuration that does not touch the s electrons to be energetically favourable with respect to any configuration that does a priori. (You can consider that part of the quoted statement to be correct.) Therefore, the a priori predicted most stable configurations of certain coordination numbers are:
1. mono-, di- and tri-coordination: use 1, 2 or 3 p orbitals to form bonds; keep one lone pair in an s type orbital. (Predicted bond angle: 90∘
2. tetracoordination (no additional lone pairs): since the former is not possible, hybridise s and p orbitals to form sp3sp3 hybrid orbitals. (Predicted bond angle: 109.5∘109.5∘.) Actually, in MO terms you should consider the four ligands to supply four group orbitals whose symmetry always fits one of the three central atom’s orbitals, resulting in one lower bond energy and one higher bond energy corresponding to triple-degenerate bonds. The sp3 description is mathematically equivalent, though.
3. penta- and hexacoordination; tetracoordination with additioal lone pairs and related: attempt to form as many normal bonds with p orbitals as possible; keep one lone pair in an s orbital if possible. Use remaining p orbitals to construct four-electron-3-centre bonds to the remaining atoms. (Predicted bond angles: diverse. 90∘ going from 2e2c bonds to 4e3c bonds; 180∘ between a pair of coordinating atoms contributing to the same 4e3c bond.)
The theories I have outlined so far do not adequately predict the bond angles of water, ammonia and related compounds. Indeed, these compounds are remarkably complicated although they seem simple. The gist, however, is that a bond angle of 90∘, while being most favourable on a pure orbital basis, introduces steric strain between the outer atoms which approach each other too closely if the central atom is relatively small. To combat this destabilisation, the bond angle is extended by mixing s-contribution into the bonding orbitals - which in turn means that the lone pair will be less s-like. The ideal bond angle for dicoordinated systems based on sterics is 180∘, showing that the electronic contribution (90∘) is more important than the steric one (180∘). Larger central atoms than oxygen and nitrogen, such as phosphorus, antimony, selenium, etc., allow for smaller bond angles since the bond lengths are larger increasing the spacing between the ligands.
The reason for the special behaviour of nitrogen and oxygen is not their high electronegativity but their small size. Chlorine, which has an electronegativity similar to nitrogen, behaves as predicted for large atoms.
We hope you will enjoy this lecture.
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Conditions for drago rule
1. Lone pairs+ bond pairs = 4
2. E.N. Should be 2.5 or less than 2.5
3. Central atom contain lone pair
4. Atom should be belong to 3,4,5, and 6 but not 2.
May be it help u
Thanks a lot sir u awesome. And cool teacher. ✌✌
In 4th point lemme correct you a bit; the central atom must belong to group 13,14.15 or 16 but not from 2nd group.
Thank you
Biopenguin let me correct u too
It is not group it is periods
@@chetalirathore3977 14th Period matlab kya . Kehna kya chahte ho bhai 🤣🤣🤣
4. Any of the elements from groups 13, 14, 15, 16 or from the 3rd to 7th period forms the central atom.
Condition for Drago's rule :-
1.If the central atom has /contains atleast 1 lone pair
2. If the central atom has no. of sigma bonds + lone pairs =4 (sp3 hybrization)
3.If the central atom has electronegativity
Surrounding atom have very small size like hydrogen
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Physics k ashis arora sir
Physics k ashis arora sir
Full sylabus nahi hai unfortunately
I watched ur 3 videos Drago rule ,bent rule and stability of carbonate salts.So clear explanation even below average students can get it . keep it up.Accept my love , care and respect sir.
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I think in 4th condition you said groups instead of period
You can also explain this on the basis of inert pair effect...down the group ns2 don't want to leave their s orbital due to high nuclear charge and poor shielding.
Thanks bro
Any of the elements from groups 13, 14, 15, 16 or from the 3rd to 7th period forms the central atom.
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Yes sir please
Please explain MOT
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Kahan pe milta hai mujhe bhi chahiye
Super sir. But sir why Cos=s/s-1 .plz tell me.
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Thankew
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order of nucleophilicity among Nh3, Ph3, Ash3 and Sbh3 considering drago's rule
One of the finest teacher for organic and inorganic 😍
Nice methodology to explain concepts of inorganic chemistry my teacher also explained a bit about this rule but only upto the bond angle part but i want a clear cut and wide explanation which i got frm u sir. Thank u & keep teaching in this way we will always support u😎
Really nice ,lot of concept, thanks a lot
A must watch lecture for students aspiring competitive exams...
sir at 8:00 and the description you are saying that central element must belong to group 13, 14,15 and 16..and at some points you are saying that they should belong to grp 3,4,5..m getting confused sir.. please get it cleared
Aise teachers shuruat se milte to kitna acha hota yaar maja aajata
First time I can easily understand and relevant, easy answer😍😍
From Bangladesh 🇧🇩
MKA guruji OPP!!! revised hogya pura drago rule :)
SIR,
your video is really good and HELPFUL to us..........BUT why do you stop to upload your video?please upload before our exam.
Sir couldn't understand the formula cos(theta)=s/(s-1). please explain from where this formula came....
I'm also with u my friend.
Are you crazy? Study what is in syllabus. U can't learn everything in 12th
Perfect explanation I am a fan of you sir
Tq very much sir for giving
Veri unique lecture
Ur teaching style very much easy and interested
Ok i got it no hbdisation in ph3 Ash3 sbh3 same with s se te. Pure s orbital with 94 percent s character which is not exist as hbd and l.p. more close to nucleus therefore no donation of es happens meaning less basicity.Thanx again ☺
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Finally i understand drago rule thankew sir..
In jd Lee book they gave surrounding atom should have en less-than 2.5 , but u said central atom En , give clarity
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Crystal ❄️ clear concept🗓️.
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Sir,woh cos94 degree =s/s-1 kyu hua ??
Sir plz upload more videos on chemistry chapter... Aapke channel mein itna kam videos kyun hai.. We need it badly... Plz sir upload more & more videos..
Thoroughly explained
simple and up to the mark explanation
Sir if question is asked in jee adv about the hybridization of PH₃ then should it be sp3.
Percentage s character 6into 3 total 18percent hoga. Therefore s character of lp is 72percent.
Good sir🥰😋🥰 ap apni book ka link to descripation mn send kar daiy.
sir.i hve a query hw we find effective nuclear charge ... as for Na (11) is :+2.2
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By the way what was ur AIR in jee?
28
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Sirji is this channel for jee preparation ?
Sir electronegativity of surrounding atom is less than or equal to 2.5 hoge not central atom.
Crystal clear
Thanks
Dear sir, does scl2 undergoes hybridization? ( H2S does not participate in hybridisation, so, I feel that SCl2 will also does not involve in hybridization).
Please clarify it sir
Sir please do revision on Chemical equilibrium for IIT?
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I want it very much please give a video on solubility
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Superb.. Osm perfect explanation
Thanks a lot sir.
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Super lecture on drago's rule.....
you are doing very appreciative work sir
Nice explanation 👍👍👏
Sir apne book likhi hai, so are you phd in chemistry???
Plz can you check for these points
1. Shouldn't the electronegativity of surrounding atom be less than 2.5 ? If as per the rule you said, central atom should have electronegativity less than 2.5 then Sulphur & selenium have electronegativity greater than 2.5 then why they don't show hybridisation.
2. The drago's rule is applicable for group 15,16,17 as group 13,14 do not have lone pair. If they have lone pair can you plz give any example?
Sir
where i will get your book on chemical bonding?
sir, as u said the lewis base character decreases down the grp in grp 15(acc. to drago rule) but in grp 16 lewis base character increases down the grp what is the exact reason for this phenomena. I asked this question particularly because u said it applies in grp 16(oxygen family) too.
Hope to get an ans soon :)
Sr u told that group 3-4-5shud b there but nitrogen phosphorus... Belong to group 15😅...please explain
Refer to old convention i.e. gr13=3A , gr14=4A and gr15=5A etc.
Sb is antimony...
Astatine is At... This was mistakenly mixed up at 12.57...
sir apne bond angle k trick meh Ph3 ,AsH3 aur SbH3 ka bond angle dushra bataya tha.. kya uska approx value liya apne?
Sir PH3 Dilute HCL ke sath rxn nhi kr rha h but agar concentrates HCL use krte h to rxn ho jata h aisa kyu hota h....sir plz reply me..
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wow
Never thought this would be yhe reason behind all the things my sir told to remember. ! :0
Sir y jo drago rule h y sirf 13 14 15 16 k hydrides k liye hi h ka ya or bh compounds 13 14 15 16 group k ise follow krte krte hn
aman Singla bro i think u didnt heared the first 2 -3 sentences what sir had said about the application of dragos rule
Dear Sir where from your book is available.
Sir please upload video on schrodinger wave equation as it is very important and no resource is available for it.
Sir please explain kinetic molecular theory of gas
sir mai bahut lucky hu ki mujhe aapka video mila.
thank you so much .
Sir %age s character is directly proportional to electronegativity bhi hota hai na to fir electronegativity hai kyu nahin hai in PH3 at 16:16!????
Bahut dhanyavad sir
It should be from 3,4,5,6 period and not from 2 period ............. 8:12 is it wrong? 🤔
Pls reply if someone know about it.
Yes
Wilkinson's reagent m phosphine ligand h sir
S
At 14:30 YOU USED DRACO'S RULE TO EXPLAIN DRACO'S RULE
Aeii88
Hahah. Jd lee main hai yeh
Sir simple overlapping nh3 me kyu Nahi ho Rahi hai
Very nice explanation sir
Good afternoon sir,
Why does simple overlapping not takes place in ammonia (NH3)?
bakwaas sawal
Sir where to buy the book written by you? I have searched in many online websites..But cannot find.please help me out
Please please make videos on States of matter and thermo.
Sir please explain energetics of hybridization
Loved it!
Sir very very nice explanation.
Sir no need of hybridization means what that the hybridization doesn't exist or we will not consider it please help