![]() ![]() ( ii) Pi bond between the two atoms is formed only in addition to a sigma bond. It is because of the fact that overlapping of atomic orbitals can take place to a greater extent during the formation of sigma bond whereas overlapping of orbitals occurs to a smaller extent during the formation of pi bond. ( i) Sigma bond is stronger than pi bond. The electrons involved in the p-bond formation are called -electrons. The pi bond consists of two charge clouds above and below the plane of the atoms involved in the bond formation. The orbitals overlap takes place in such a way that their axes are parallel to each other but perpendicular to the internuclear axis. ![]() This type of covalent bond is formed by the lateral or sidewise overlap of the atomic orbitals. It is because of the fact, that p-orbitals allow overlap to a greater extent as compared to p- s which is larger as compared to s- s overlap. The strength of three types of sigma bonds varies as follows : The s- s, s- p and p- p overlaps have been shown diagramatically in Figure below. It involves mutual overlap of half-filled p-orbitals of the two atoms. It involves mutual overlap of half-filled s-orbital of the one atom with half-filled p-orbital of the other. It involves mutual overlap of half-filled s-orbitals of the atoms approaching to form a bond. There can be three types of axial overlap as discussed below : The electrons constituting sigma bond are called sigma electrons. The electron cloud formed as a result of axial overlap is cylindrically symmetrical about inter-nuclear axis. The atomic orbitals overlap along the inter-nuclear axis and involve end to end or head on overlap. This type of covalent bond is formed by the axial overlapping of half-filled atomic orbitals. ( a) Sigma covalent bond ( b) Pi covalent bond. The covalent bonds can be classified into two different categories depending upon the type of overlapping. It has already been discussed that the formation of a covalent bond involves the overlapping of half-filled atomic orbitals. Diols and triols are much more soluble than mono hydroxyderivatives because they form more effective hydrogen bonding. In case of ROH & ROR their solubility in water is almost same because both show H-Bonding with H 2O. For example NH 3 is more soluble in H 2O than PH 3, ROH are more soluble in H 2O than RSH due to association. In the system where solute and solvent particals shows association with H-Bonding are more soluble than other combination. It is very minor factor which control solubility of compounds. increases with the rise in temperature whereas that of Na 2SO 4 decreases with the rise in temperature.Ħ. For example, the solubilities of KNO 3, NaNO 3, KCl, NH 4Cl etc. In equation (1) the solublility decreases with the rise in temperature. This is the case with most of the solid- liquid solutions, where the solubility increases with rise in temperature. e., a rise in temperature) in equation (2) causes more of the solute to dissolve. (1)Įndothermic : Solute + Solvent + Heat Solution. Formation of a solution may be exothermic or endothermic process and may be represented as follows :Įxothermic : Solute + Solve Solution + Heat. ![]()
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