Chemical Bonding PDF

# Chemical Bonding ## Chemical Band | Strong Bonds (≥ 200 KJ) | Weak Bonds (2 to 40 KJ) | |---|---| | ① Covalent Bond | Vanderwaals Force (2 to 10 KJ) | | ② Ionic Bond | Hydrogen Bond (10 to 40 KJ) | | ③ Co-ordinate Bond | | | ④ Metallic bond | | * **Covalent Bond** - mutual sharing of e° * **Ion...

# Chemical Bonding ## Chemical Band | Strong Bonds (≥ 200 KJ) | Weak Bonds (2 to 40 KJ) | |---|---| | ① Covalent Bond | Vanderwaals Force (2 to 10 KJ) | | ② Ionic Bond | Hydrogen Bond (10 to 40 KJ) | | ③ Co-ordinate Bond | | | ④ Metallic bond | | * **Covalent Bond** - mutual sharing of e° * **Ionic Bond** - complete transfer of e° * **Co-ordinate Bond** - shared ee pair is contributed by only one atom. * **Metallic Bond** - Force between kernel and Free ee. ### Lewis Dot structure: 1. Identify the central atom and surrounding atom. 2. Assign -ve charge to more electronegative atom and +ve charge. 3. O atom form two bonds but o form one bond. 4. Try to complete octet and duplet of all atoms. 5. But if central atom contains vacant d-orbital such as P.S, a etc then octet can expand. #### Examples: 1. C104 ``` :O: || CI = O || :O: ``` 2. CO32- ``` :O: || C || :O: ``` 3. NO3- ``` :O: || N - O: || :O: ``` 4. HND2 ``` H | H | O = N = O ``` 5. NH4+ ``` H | H - N - H | H ``` 6. CO2 ``` O = C = O ``` 7. SO42- ``` :O: || O - S - O || :O: ``` 8. PO43- ``` :O: || O - P - O: || :O: ``` * **Formal charge:** Formal charge = Valence e - lone pair e - no. of surrounding bonds * **Bond order From Resonance:** B.O = Total no. of Bonds / Total no. of positions * **Average Formal charge on surrounding atom:** Net charge on species / no. of surr. atoms * **Valence Bond Theory (VBT):** 1. A covalent Bond is a result of overlap of atomic orbitals of two atoms. 2. The atomic orbitals which overlap must contain unpaired electron with opposite spins. Also they must possess either same or nearly same energies. 3. Strength of covalent bond α extent of overlap. #### Two types of overlap * **Head to Head (axial)** - Result in σ bond. * **Side wise (lateral)** - Results in π bond. * The direction of orbital overlap decides geometry of molecule formed. * The maximum no. of covalent bonds formed by the particular atom are equal to number of the unpaired electron in its ground state. * **Types of overlap:** 1. **S-S overlap** - H2 formation - Always form σ bond. 2. **p-p overlap** - Cl2, F2, 02 - (σ) (σ) (σ and π) - Can Form σ and π bond. 3. **s-p overlap** - HCl Formation - always form σ bond. - CHF Formation - no σ bond * **Strength order:** IS-IS > IS-2P > 2p-2p > 2S-2p > 2S-2S > 3P-3P > 3S-3P > 3S-3S * **Concept of Hybridisation (modified VBT):** The mixing and recasting of atomic orbitals of same atom to form new orbitals called hybrid orbitals which are identical in all respect. * **Types of hybridisation:** 1. **sp - (2) - Lineat** 2. **sp2 - (3) - Trigonal planar** 3. **sp3 - (4) - Tetrahedral** 4. **sp3d - (5) - Trigonal Bipyramidal** 5. **sp3d2 - (6) - octahedral** 6. **sp3d3 - (7) - Pentagonal Bipyramidal** 7. **dsp2 - (4) - Square planat** 8. **d3s - (4) - Tetrahedral** 9. **dsp³ - (5) - Trigonal Bipyramidal** 10. **d2sp3 - (6) - Octahedral** 11. **d3sp3 - (7) - Pentagonal Bipyramidal** 12. **sp2d - (4) - square planat** * **Method of Finding hybridisation:** * **X** - Indicate valencere of central atom. If surrounding atom is monovalent (H,F,Cl, Br, I, etc) then allot 1 'X' form 1 atom. If surrounding atom is divalent (O,S) then allot 2'x' Form 1 atom. **Examples:** * H = bond + no. of lane pait * `H=2` (`sp`) * `H=4` (`sp3d`) * `H=3` (`sp2`) * `H=6` (`sp3d2`) * `H=7` (`sp3d2`) - (more complex structure) * **Valence shell electron pair repulsion (VSEPR Theory):** 1. If central atom is surrounded by only bond pairs and no lone pairs then geometry and shape both are same. ex. CH4. 2. If central atom is surrounded by both bond pairs and lone pairs then geometry and shape both are different. 3. The order of repulsion of various types of ee pairs is `lp-1p > lp-bp > bp-bp`. 4. Lone pair of central atom reduces bond angle from expected value. Decrease in bond angle from expected value × no. of lone paies on central atom. * **Code number Hybridisation Geometry Shape** * `200` `sp` Linear Linear (lιn2, BeCl2) * `330` `sp2` Trigonal planar Trigonal planat (BF3) * `321` `sp2` V-shape (SNC13) * `440` `sp3` Tetrahedral Tetrahedral (CH4) * `431` `sp3` Pyramidal (NH3) * `422` `sp3` V-shape (H2O) * `550` `sp3d` TBP TBP (PC15) * `532` `sp3d` See-Saw (SF4) * `541` `sp3d` T-Shape (CIF3) * `660` `sp3d2` Octahedral Octahedral (SF6) * `623` `sp3d2` Linear (XeF2) * `651` `sp3d2` Square pyramidal (Brfs) * `642` `sp3d2` Square planak (XeF4) * `770` `sp3d3` PBP PBP (IF7) * `761` `sp3d3` Distorted octahedral * `752` `sp3d3` Pentagonal planar. * **Bond parameters (measurable properties of covalent bond):** 1. **Bond angle** - angle between two adjacent covalent bonds. 2. **Hybr expected B.A B.A x % Sy character (His diff)** * `sp` `180°` `sp` `50%S` * `sp2` `120°` `sp2` `33.33% S` * `sp3` `109°28' -` `sp3` `25%. S` * `sp3d` `90°, 120'` * `sp3d2` `90°, 180'` * `sp3d3` `90°, 72` * `dsp2` `90°` 3. **No. of lone pairs** * **I Same - Hybridisation, surrounding atom** **Different - central atom, no. of lone pairs then** **B.A x** **ex: CH4 > NH3 > H2O** * **II Same - Hybridisation, surrounding atom, lone pair** **Different - central atom** **B.A x EN of central atom** **NH3 > PH3 > ASH3> S6H3** **H2O > H2S > H2Se > H2Te** * **III Same - Hybridisation, central atom, lone pair** **Different - Surrounding atom** **B.A x EN of surr. atom** **F20 < C120 < BY20** * **Bond order : The number of bonds between two atoms. calculate by using any of the following:** 1. **MOT** - Total e≤20, species is diatomic. 2. **Resonance** - BD = total no. of Bonds / total no. of positions. 3. **Use structure.** * **Bond energy: Energy required to break 1 mole of particular bonds.** 1. **Bond energy α Bond multiplicity** 2. **Bond energy α %s character** 3. **Bond energy α 1/ Atomic size** 4. **Bond energy α Bond polarity** 5. **Bond energy α no. of lone pairs** - use this factor when there is single bond betin 2 identi. bom * **Big exception: in halogens** **Expected order**: F-F > CI-CI > Br-Br > I-I **Actual order**: CI-CI > Br-BY > F=F> I-I * **Band length: The distance between the centres of nudei of two closely bonded atoms** 1. **Bil α Bond multiplicity** 2. **B.LX Atomic size** 3. **B.LX %s - character** 4. **B.LX Bond order** - ex: 02, 03, H202 * `B.O` (it has a yu bo tongb) **Bond length** * `CO2` `2` * `CO32-` `1.33` * `CO` `3` * `CO2` * `CO3^2-` * `CO` * **Dipole moment : Measure of polarity of bond** **u = q x r** **Units: esu.cm, c.m, Debye** **1D = 10-18 esu** **1D = 3.33 X 10-30 cm** **MR = √ M1² + M2² + 2M1M2 cosθ ** **% ionic character = u observed x 100 / u theory** **Polar molecule = MR≠0 (permanant dipole moment)** **Non-polat molecule = MR = 0** * **Molecular orbital theory:** (Applicable only for diatomic species having total e≤ 20) 1. During molecule or ion formation through covalent bonding, Atomic orbitals combine together to form new orbitals called molecular orbitals. 2. The number of molecular orbitals formed are exactly Jequal to number of Atomic orbitals combined. 3. Two types of Molecular orbitals formed: * **Bonding Mo.** (denoted by σ and πι) * **Anti-Bonding MO.** ( denoted by σ* and π*) 4. **AD's combined BMO'S combined ABMO'S formed** * `ns + ns` `σns` `σ* npz ` * `npz + npz` `σnpz` `σ* npz` * `прx + проæ` `πпрx` `π* прx` * `пру + пру` `πпру` `π* пру` * **Filling of electrons in Mo's:** 1. **Configuration I: when total e≤ 14.** ex: N2, N2+, B2, C2 etc (25-12p mixing occurs) `61s < 6*1s < 625 6*25 < π2px = π2py < 62pz < π* 2px = π* 2py < 6*2pz` **BABA BBB AAA** 2. **Configuration II: when total ee = 15 to 20 exclay** ex: 02, 02, F2, Ne2 etc (25-2p mixing do not occurs) `61s < 6*1s < 625 6*25 < 62P2 < π 2px = π2py < π* 2px = π* 2py < 6*2pz` * **Applications of MOT:** 1. **Bond order = B.O = 1 (Nb-Na) If B.O = 0 species do not exist. B.O≠0 species exist.** 2. **Total ee B.O** * `1` `0.5` * `2` `1.0` * `3` `0.5` * `4` `0` * `5` `0.5` * `6` `1.0` * `7` `0.5` * `8` `0` * `9` `0.5` * `10` `1.0` * `11` `1.5` * `12` `2.0` * `13` `2.5` * `14` `3.0` * `15` `2.5` * `16` `2.0` * `17` `1.5` * `18` `1.0` * `19` `0.5` * `20` `0` **exception:** * `CO+ = 3.5` * `NO+ = 3.5` 3. **Band length α 1/ Bond order** 4. **Band energy α Bond order** 5. **Bond strength α Bond order** * **Thermal stability** 6. **Prediction of magnetic nature:** * `Total ee are odd or 10 DY 16` → **Paramagnetic** * `Total eo are even` → **Diamagnetic.** * **Ionic Bond:** (The Bond which is formed by complete transfer of ea from one atom to another atom). 1. `ΔΕΝ > 1-6` 2. `LOW IE of element forming cation.` 3. `High electron: gain enthalpy with -ve sign of element forming anion.` 4. `High Lattice enthalpy."` 5. `Overall decrease in energy of system.` * `IE (+ve)` * `Aegt (-ve)` * `LE (-ve)` * **Imp. note:** 1. The Bond Formed between metal and non metal is generally ionic. 2. The Bond Formed between two complex ions or in between simple ion and complex ion is also ionic. 3. There are some substance which contains imic, covalent as well as co-ordinate bond. * `ex: NH4CI` * `[Ni(H2O)6] SO4` * **Electrovalency: no. of electron lost or gained by one atom.** * **Lattice energy or lattice enthalpy (ALH)** Amount of energy released when 1 mole of ionic compound is formed from constituent gaseous cation and gaseous anion. ** ΔιΗ = -ve.** or Amount of energy requrited to break I mole of ionic compound into its constituent gaseous cation and gaseous anion. **ΔιΗ = +ve.** * **V. Imp:** 1. **stability of ionic compound α ΔιΗ.** 2. **solubility of ionic compound in H20 α 1/ ΔιΗ** 3. **ΔιΗ α 90.ga** **Yc+Ya** * **covalent nature in ionic bond: (concept of polarisation)** * **For cation** → **polarising power.** * **For anion** → **polatisibility** * **Covalent character in ionic substance α extent of polarisation** * **Fajan's rules:** 1. **Polarisation α size of anion** * **small cation** **SHILA** **Large anion** 2. **Polarisation α size of cation** * **High charges** 3. **Polarisation α 9c and ga.** * **Polarising power is exceptionally more if cation posess pseudo inert gas configuration (nsanpind 19)** * **ex: Nax < cu'x, KX < Agx** * **V.Imp:** * **ths & bavajmo simi to utilidate** * **Melting point; thermal stability, on sinui folutitidulae** * **ionic natute, solubility in H20** * **Apiop Polarisation H:Ys** * **ortor** * **(asitoairoloq to typonds): bond sindi oi asuta Jaslovs** * **mian batriotaib** * **mian Losintomampa** * **sowon priciolog mitos 207** * **philidisiaplog ←← noino 107** * **witsaaplog to tastxa & spantadua singi ni satrasado duelovao** * **AJIHE pros Moma** * **avin mito adina to asia so mitovan 109** * **mitus to asie op bao op mitosbo109**