Presentation on theme: "Valence-bond theory. The remaining 2p orbitals cannot merge to give a bonds as they do not have cylindrical symmetry around the internuclear axis. Instead,"— Presentation transcript:
The remaining 2p orbitals cannot merge to give a bonds as they do not have cylindrical symmetry around the internuclear axis. Instead, they merge to form two bonds. A bond arises from the spin pairing of electrons in two p orbitals that approach side-by-side (a bove).
Polyatomic molecules Each bond in a polyatomic molecule is formed by the spin pairing of electrons in atomic orbitals with cylindrical symmetry about the relevant internuclear axis. Likewise, bonds are formed by pairing electrons that occupy atomic orbitals of the appropriate symmetry. Bisakah kalian menjelaskan pembentukan ikatan pd H 2 O ?
Another deficiency of VB theory is its inability to account for carbon's tetravalence (its ability to form four bonds). The ground-state configuration of C is ;, which suggests that a carbon atom should be capable of forming only two bonds, not four. Bagaimana untuk mengatasi kekurangan ini? promotion Masalah (karakter orbital) ?
a hybrid orbital The specific linear combinations that give rise to four equivalent hybrid orbitals are
Because each hybrid is built from one s orbital and three P orbitals, it is called an sp 3 hybrid orbital. The (un-normalized) wavefunction for the bond formed by the hybrid orbital h 1 and the 1s A orbital (with wave function that we shall denote A) is An sp 3 hybrid orbital formed from the superposition of s and p orbitals on the same atom. There are four such hybrids: each one points towards the corner of a regular tetrahedron. The overall electron density remains spherically symmetrical.
Each sp 3 hybrid orbital forms a bond by overlap with an His orbital located at the corner of the tetrahedron. This model accounts for the equivalence of the four bonds in CH 4. A more detailed representation of the formation of an sp 3 hybrid by interference between wavefunctions centred on the same atomic nucleus. (To simplify the representation, we have ignored the radial node of the 2s orbital.)
Bagaimana menjelaskan struktur ethena? Forms of sp 2 hybrid orbitals: (a) An s orbital and two p orbitals can be hybridized to form three equivalent orbitals that point towards the corners of an equilateral triangle. (b) The remaining, unhybridized p orbital is perpendicular to the plane.
A representation of the structure of a double bond in ethene; only the bond is shown explicitly.
Teori orbital Molekul (MO = Molecular orbital theory) Dlm teori MO, elektron tidak dianggap sebagai milik ikatan khusus tetapi diperlakukan menyebar seluruh molekul. a. The hydrogen molecule-ion The hamiltonian for the single electron in H; is
The one-electron wavefunctions obtained by solving the Schrodinger equation H = E are called molecular orbitals (MO). A molecular orbital gives, through the value of, the distribution of the electron in the molecule. A molecular orbital is like an atomic orbital, but spreads throughout the molecule. (a) Linear combinations of atomic orbitals If an electron can be found in an atomic orbital belonging to atom A and also in an atomic orbital belonging to atom B, then the overall wavefunction is a superposition of the two atomic orbitals: ………………….7 )
The technical term for the superposition in eqn 7 is a linear combination of atomic orbitals (LCAO). An approximate molecular orbital formed from a linear combination of atomic orbitals is called an LCAO-MO. A molecular orbital that has cylindrical symmetry around the internuclear axis, such as the one we are discussing, is called a orbital because it resembles an s orbital when viewed along the axis and, more precisely, because it has zero orbital angular momentum around the internuclear axis. A general indication ofthe shape of the boundary surface of a orbital.
Self-test 3 Normalize the orbital - in eqn 7.