Chem Bonding I

In order of importance • no. of bonds b/w atoms (triple>double>single) - more 2- to share b/w atoms - atoms held closer • Extent of atomic orbital overlap (smaller - more effective overlap vs larger - more diffuse & less effective overlap) • Polarity of bond - polar>non-polar due to extra electrostatic attraction b.w partial charges • Presence of neighbouring lone pairs - very small atoms (P2 elements) have lone pairs in close proximity - excessive repulsion that weakens the covalent bond

Diff electronegativities of the 2 atoms - unequal sharing of e- by the 2 bonded atoms - permanent dipole is formed n the bond is polar - with this separation of charge, the covalent bond is said to have some covalent character

• Greater ratio of e- to protons - the outer e- of the anion is loosely held to the nucleus • The cation, being +vely charged - e- deficient - attract the outer e- of the anion • Attraction distorts the e- cloud in the anions - polarising it to some extent • Shifts the e- density from the anions towards the cations - bonding e- may be considered partially shared b/w the ions - has some covalent character

• Polarising power of the cation (ability to polarise the anion) ∝ charge density ∝ charge of cation/cation radius • Polarisibility to the anion (ease of being polarised) ∝ size

e- pairs 0LP 1LP 2LP 3LP 2 linear 180 3 trigonal bent planar 120 117 4 tetrahedral trigonal bent 109.5 pyramidal 105 107 5 trigonal see-saw T-shaped Linear bipyramidal 120 & 180 90 & 180 180 120 & 90 6 octahedral sq. sq planar 90 pyramidal. 90 90

LP vs BP • LP exert greater repulsion than BP as • LP are closer to the nucleus of an atom since they are attracted by only 1 +ve nucleus compared to bp which are attracted by 2 nuclei • Hence, LP occupy a larger vol in space since they are not shared b/w 2 atoms - greater repulsion 2. Electronegativity (use when molecules have same no. of bp/lp) • N is > electronegative than P - bp of e- are drawn closer to N • greater repulsion b/w bp in NH3 3. Steric repulsion (size - use when shape is the same) • size of terminal atoms increases, increase in e- clouds, increase in repulsion b/w bp

instantaneous dipole - induced dipole attraction • e- move constantly and randomly in an atom/molecule causing uneven distribution of e- • the portion with more e- acquires a partial -ve charge while the other portion acquires a partial +ve charge • this dipole induces a dipole in neighbouring molecules • an electrostatic attraction thus occurs b/w oppositely charged molecules • such attractions are always weak and short-lived since the unequal distribution of e- last only for a split second • id-id interactions are forming and breaking all the time

• • No of e- • larger e- clouds have longer momentary distortion and are more easily polarised - stronger id-id interactions 2. surface area of contact b/w molecules • id-id are weak and short-ranged • for molecules with comparable no. of e-, straight chair molecules have a greater SA and hence more extensive id-id interactions as compared to a near-spherical, branched molecule

Permanent dipole - permanent dipole attractions (in polar molecules) • More electro-ve atoms acquire a partial -ve charge • Less electro-ve atoms acquire a partial +ve charge • partial +ve charge end aligns near the … -ve end of the neighbouring molecule • electrostatic attraction b/w permanent … & … ends of the molecules is known as pd-pd

*1. Extent of hydrogen bonding - more or less extensive - u write ___(no.) no. of H-bonds per molecule - lowest no. b/w no. of H-atoms in compound & no. of LP 2. 2 scenarios: (depends on data given) 1st: Polarity of H-Y bond H-F > H-O > H-N cuz most to least polar, so strongest to weakest 2nd: WILLINGNESS to share LP on Y F > O > N most to least electro-ve least to most willing to

bond strength/no. of bonded e-

CHARGE DENSITY • Charge - greater no. of valence e- (larger charge), the stronger the metallic bond • Size of metal cation - for the same no. of available valence e-, the smaller metal cation will exhibit stronger metallic bonding as delocalised e- are closer to the positive nuclei, resulting in stronger attraction b/w e- and nuclei

ICL3 - pt towards I BH3 & NH3 AlCl3

Ionic > Covalent > Metallic > I-D attractions > H-bonding > Pd-pd attractions > pf-id attractions > id-id attractions (? permanent dipole-induced dipole attraction is stronger than pd-pd & id-id)

A has a ___ struc while B has a ___ struc. More energy is required to overcome the strong __ b/w __ as compared to the weak __ b/w ___

Both ___ have giant ionic struc and the strength of the ionic bond depends on the mag of LE |LE| ∝ |…| since ___ has a > sth than ___, strength of ionic bond is … and less energy is required to break the weaker ionic bonds in __, hence .. melting pt

__ struc/molecule… with ___ (IMF) b/w molecules. the energy released from the weak __ b/w __ & __ are insufficient to compensate for the energy needed to overcome the strong ___ b/w ___

There are __ e- pairs around … which consists of __ BP & __ LP. To minimise repulsion b/w the e- pairs, the shape is __ and the bond angle is ___