12/28/2023 0 Comments Explain resonance in chemistry![]() There is no free rotation of atoms around the pi bond. There is a free rotation of atoms around the sigma bond. ![]() The molecular orbital is discontinuous containing two charge cloud. The molecular orbital is continuous containing only one charge cloud. It is formed by the overlapping of p-p orbitals. It is formed by overlapping of s-s, s-p or p-p orbitals. Overlapping of orbitals takes place perpendicular to the internuclear axis. Overlapping of orbitals takes place along the internuclear axis. It is formed by sidewise or lateral overlapping of half filled orbitals. It is formed by end to end, head-on or axial overlapping of half-filled orbitals. Differences between sigma (σ) and pi (π) bonds σ – bond Greater the extent of overlapping, stronger is the bond and vice versa.Īccording to this theory, the covalency of an element is equal to the number of half-filled orbitals present in the valence shell of an atom.ĭepending upon the nature of overlapping, there are two types of covalent bond.Ī covalent bond formed due to sidewise overlapping of half filled atomic orbitals is called Pi bond. The strength of the covalent bond depends upon the extent of overlapping. ![]() Due to overlapping, the electron density between the two nuclei of the bonded atom is increased with causes the formation of a covalent bond.After overlapping, the pairing of electrons takes place which decreases energy and increases the stability of the system.For overlapping, the half-filled orbitals must have electrons of opposite spin.Covalent bonds are formed due to the overlapping of half-filled atomic orbitals are present in the valence shell of participating atoms.Following are the postulates of this theory: To explain the stability of the covalent molecule, a new method to form a covalent bond was proposed by Hitler and London. So the actual shape of molecule is angular with an angle of 105.5°. But, due to the presence of two lone pair of electrons, there is distortion in the shape because the lone pair exerts greater repulsion to the bond pair due to which contraction in bond angle takes place. So the expected shape of the molecule is tetrahedral. To minimise the repulsion between them, they should be arranged in a tetrahedral manner. The central atom O of the H 2O molecule is surrounded by 4 electron pairs. The electronegativity of atoms in a molecule also affects the bond angle of the molecule. The repulsive interaction between the electron pair follows the following order: lp-lp>lp-bp>bp-bp.Ĥ. It is due to the presence of lone pair of electrons. If the central atom of a molecule is surrounded by both bond pair and lone pair of electrons, the molecule does not have a regular shape. If the central atom of a molecule is surrounded only by a bond pair of electron, the shape of the molecule is regular. The electron pairs are arranged as far apart as possible so that there is minimum repulsion between them due to which stability is increased.Ģ. The shape of covalent molecules depends upon the number and nature of electron pair surrounding the central atom. The main postulates of this theory are given below:ġ. ![]() To predict the shape of the covalent molecule, Gillespie and Nyholm developed a theory known as valence shell electron pair repulsion theory. Resonance in NO 2 – Valence shell electron pair repulsion (VSEPR) theory It is represented by a double-headed arrow (↔).Ģ. The real structure of the molecule or ion is a hybrid of these structures called a resonance hybrid. More than one such structure of the same molecule or Ion is called resonating structure. The phenomena in which a molecule or ion cannot be represented by a single structure but represented by more than one structure to explain its properties is called resonance. ![]()
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