Vriti EdustoreChemical bonding
CHEMICAL BONDING
BOND: a force that acts b/w 2 or more atoms to hold them together as a molecule.
Reasons
- Lowerisation of energy: Bonded state is more stable coz has lower potential energy than unbonded state.
- Octet: old rule, disregarded now. Actually complete octet was assumed to be most stable.
TYPES OF BONDS
1. Chemical bond 2. Force of Attraction 3. Typical bonds
.
1. Ionic Bond or electrovalent bond
- forms when ease of formation of ions, high lattice energy
- complete transfer of e
- one ion good donor(low IE), other good acceptor(high EA)
- ΔEN increases, tendency to form I.B. increases.
- Non directional
Electrovalence: no. of e gained/ lost by any atom during bond formation (no sign)
Ionic solids are
- High melting & boiling
- Bad conductor in solid state
- Soluble in polar solvents
- Good conductor in liquid and molten state
- Isomorphous
- Crystalline
Some facts regarding ionic solids:
- Hydration of ionic solid involves evolution of heat, weakening of attractive force, dissociation into ions.
- Most of them: have 3-D network structure, do not exhibit space isomerism (non-directional bonds), and ionization is always endothermic.
2. Covalent Bonds
- Force of attraction b/w nucleus of 1 atom and e cloud of another atom
- Sharing of e
- Types: single, double, triple
: polar, nonpolar
- directional
- low melting, boiling point
- Less conducting. conduction is due to auto-protolysis / self-ionization
Covalence: no. of e involved in sharing (of any one atom)
- Coordinate bond
- Bond b/w Lewis acid and Lewis base.
- L.B. l.p. on central atom available for donation
THEORIES OF BOND FORMATION
- Kossel, Lewis approach(electronic theory of covalence)
- VSEPR
- VBT
- MOT
Lewis dot structures
- Central atom: connected to max. atoms, least electronegative, covalence>1, less in number, can’t be H or F
- e.g. Cl2O: O, ClO2: Cl, NOCl: N, N2O: N
- Exceptions of basicity: H3PO4:1; H4P2O5:2.
Naming of acids
Parent acid : 2 types, ous (lower O.S.), ic(higher O.S.)
e.g. HPO3 is metaphosphoric acid
SO3 is not metasulphurus acid actually at least one H is compulsory in acids. It’s an acid anhydride.
Ortho prefix: used for P.A.when its meta form is possible. e.g. H3BO3 is orthoboric acid. Orthophosphorous acid is an exception.(H3PO3)
Pyro prefix: 2 P.A.- (H2O). e.g. H4P2O7 is pyrophosphoric acid.
Hypo prefix: P.A.(ous )- O .e.g. H3PO2 is hypophosphorous acid.
Per prefix: P.A.(ic) +O.e.g. HNO4 is pernitric acid or peroxynitric acid(-O-O- linkage is present)
Sub: oxides for which no. of O atoms is less than no. of central atoms. E.g. C3O2
Salts of ic:ate, Salts of ous:ite. Replaceble H are involved in naming.
e.g. NaH2PO4 is sodium dihydrogen phosphate but NaHPO3 is sodium phosphate.
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