NotA Visual

Lewis Symbol Octet rule

Rules of writing Lewis structure

No. of 1. 2. 3. Odd
valence e- Incomplete Expanded no. of e
octet octet
Example <8 No. of 5,
>8 7, 9
Be, B, Al
Element Usually
in Period odd
3 or > numbered
group

•1. Noble d10 •3. Half-
gas filled
configur • 2.Pseudo orbital
ation noble configur
gas ation
ns2 np6 configur
ation d5

How to Formal charge = 2 or more Lewis structures which can be written for a single
calculate formal no. of valence e- - [no of lone pair e- + ½ bonding pair e-] molecule, but no one structure can accurately represent the

charge? actual structure

Most plausible All zero F.C. (neutral molecules) Polyatomic
resonance Has the lowest F.C. ions
structure?
-ve F.C. on more electro-ve atom

TYPES OF BONDING

Ionic @ Electrovalent Covalent Bond Dative @ Coordinate Bond
Bond

Electrostatic force of attraction Bond formed by a pair of e- Covalent bond in which the shared
shared between two atoms. pair of bonding e- are contributed by
between cation and anion in an ionic only one of the bonded atoms.
compound. 3 types of bond:
Donor
Metal Non- Bond length: atom Contains lone
atom metal ≡< =<–
atom pair of e-
+ Example:
- Dative
+ve ion bond
(cation) -ve ion
(anion) Acceptor
atom Contains empty
+ Ionic - orbital in valance
bond shell to accept the
cation anion e-pair

Example: Example:

VALENCE SHELL ELECTRON PAIR
REPULSION (VSEPR)THEORY

The e- pairs Used to predict the depends
surrounding a central shape of covalent on
molecules and
atom will repel one polyatomic ions The no. and geometric
another and arrange arrangement of e-

themselves as far pairs around a central
apart as possible in atom
order to minimise the
lone pair – bonding pair –
repulsion bonding pair bonding pair

e- GROUP REPULSION

lone pair –

lone pair

Molecular geometry

Polar bond Deducing polarity of molecules

A bond between atoms of different Bond dipole can cancel each other Bond dipole can cancel each other
electronegativity in which the Molecule geometry linear (symmetrical) Molecule geometry square pyramidal
Resultant dipole moment, μ = 0 (symmetrical)
distribution of the density of the Therefore: non polar molecule Resultant dipole moment, μ > 0
bonding e- pair is unequal. Therefore: ____________ molecule

Dipole moment, μ Bond dipole can not cancel each other
Molecule geometry _______________
A quantitative measurement of the (symmetrical)
polarity of a bond. Resultant dipole moment, μ > 0
Therefore: ___________ molecule
μ=Qxr
Bond dipole can not cancel each other
Polar molecule Molecule geometry see saw
(unsymmetrical)
A polar molecule contain polar Resultant dipole moment, μ ___ 0
covalent bond(s) and Therefore: __________molecule

it has non-zero resultant dipole
moment (µ >0).

Resultant dipole moment, μ

Determine by molecular geometry
(symmetrical/unsymmetrical) and

bond polarity
μ > 0 polar molecule
μ = 0 non polar molecule