Hybridization & VSEPR Theory for Bond Angles (Chemistry)

Hybridization and VESPR theory, molecule shapes Chemistry Mr. Miller Hybridization In chemistry, orbital hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond t...

Hybridization and VESPR theory, molecule shapes Chemistry Mr. Miller Hybridization In chemistry, orbital hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory. Types of Hybridization Based on the types of orbitals involved in mixing, the hybridization can be classified as sp, sp2, sp3, sp3d, sp3d2, sp3d3. Let us now discuss the various types of hybridization, along with their examples. sp Hybridization sp hybridization is observed when one s and one p orbital in the same main shell of an atom mix to form two new equivalent orbitals. The new orbitals formed are called sp hybridized orbitals. It forms linear molecules with an bonding angle of 180°. Important : A atom that is SP hybridized is bonded to two different atoms Each sp hybridized orbital has an equal amount of s and p character – 50% s and 50% p character This type of hybridization involves the mixing of one ‘s’ orbital and one ‘p’ orbital of equal energy to give a new hybrid orbital known as an sp hybridized orbital. sp hybridization is also called diagonal hybridization. Examples are in molecules such as ethyne sp Hybridization 2 sp2 hybridization is observed when one s and two p orbitals of the same shell of an atom mix to form 3 equivalent orbitals. The new orbitals formed are called sp2 hybrid orbitals. All the three hybrid orbitals remain in one plane and make an angle of 120° with one another. Each of the hybrid orbitals formed has a 33.33% ‘s’ character and 66.66% ‘p’ character. Important- Atoms that are Sp2 hybridized has 3 atoms bonded to it. Or two atoms and a lone pair of electrons. A mixture of s and two p orbitals formed in shape of trigonal symmetry and is maintained at bond angle of1200. The molecules in which the central atom is linked to 3 atoms and is sp2 hybridized have a triangular planar shape. sp2 hybridization is also called trigonal hybridization. It involves mixing of one ‘s’ orbital and two ‘p’ orbital’s of equal energy to give a new hybrid orbital known as sp2. Examples of sp Hybridization 2 All the compounds of Boron i.e. BF3, BH3 All the compounds of carbon-containing a carbon-carbon double bond, Ethylene (C2H4) SP3- Hybridization: Formation of four sp3 hybrid orbitals from one 2s and three 2p orbitals. The sp3 orbitals point to the corners of a tetrahedron Sp3 orbitals in carbon allows for 4 single bonds to be made Degenerate Hybrid orbitals SP hybrization Examples of sp Hybridization: All compound s of beryllium like BeF2, BeH2, BeCl2 All compounds of sp Hybridization 3 When one ‘s’ orbital and 3 ‘p’ orbitals belonging to the same shell of an atom mix together to form four new equivalent orbital, the type of hybridization is called a tetrahedral hybridization or sp3. The new orbitals formed are called sp3 hybrid orbitals. These are directed towards the four corners of a regular tetrahedron and make an angle of 109°28’ with one another. The angle between the sp3 hybrid orbitals is 109.280 Each sp3 hybrid orbital has 25% s character and 75% p character. Example of sp3 hybridization: ethane (C2H6), methane and ammonia. Tetrahedral shape of sp3 hybridized molecule  VESPR Theory- Valence shell electron pair repulsion model- used to determine bond angles, shapes and hybridization 104.5 Lets draw the sp3 hybrid structure of ammonia Question what is the lewis structure, hybridization, bond angle and shape of : (i) H2O (ii) CO2 (iii)CCl4 Steps : sketch Lewis structure first and apply it to formula. sp d Hybridization 3 sp3d hybridization involves the mixing of 1s orbital, 3p orbitals and 1d orbital to form 5 sp 3d hybridized orbitals of equal energy. They have trigonal bipyramidal geometry. The mixture of s, p and d orbital forms trigonal bipyramidal symmetry. Three hybrid orbitals lie in the horizontal plane inclined at an angle of 120° to each other known as the equatorial orbitals. The remaining two orbitals lie in the vertical plane at 90 degrees plane of the equatorial orbitals known as axial orbitals.  Example: Hybridiza tion in Phosphorus pentachloride (PCl5) sp d Hybridization 3 2 sp3d2 hybridization has 1s, 3p and 2d orbitals, that undergo intermixing to form 6 identical sp3d2 hybrid orbitals. These 6 orbitals are directed towards the corners of an octahedron. They are inclined at an angle of 90 degrees to one another. Shapes of molecules -VSEPR theory The valence shell electron pair repulsion theory (VSEPR theory) can be used to work out the shapes of molecules. It uses the following rules: Pairs of electrons in the outer shells of the atoms in a molecule repel each other and move as far apart as possible. This minimizes repulsive forces in the molecule. Repulsion between lone-pairs and lone-pairs (of electrons) is greater than the repulsion between lone-pairs and bond-pairs of electrons. Repulsion between lone-pairs and bond-pairs (of electrons) is greater than the repulsion between bond-pairs and bond-pairs of electrons. Shapes of molecules with only single bonds The information below shows how VSEPR theory is used to work out the shapes of various molecules. /bent Shapes of molecules and compound ions with multiple bonds The information below shows how VSEPR theory is used to work out the shapes of carbon dioxide as well as oxo ions (those containing oxygen and another non-metal) Predicting the shapes an bond angles of molecules similar to ethane such as Simple substituted derivatives, for example, dichloroethane Ethane C2H6 C2H4Cl2 C2H4