Molecular Orbital Theory Hybridization Dr Seemal Jelani Chem-160 2/27/2019

Molecular orbital theory is concerned with the combination of atomic orbitals to form new molecular orbitals New orbitals arise from the linear combination of atomic orbitals to form bonding and antibonding orbitals Bonding orbitals -------------------- lower energy Antibonding orbitals--------------- High energy Dr Seemal Jelani Chem-160 2/27/2019

The valence bond theory is an extension of the Lewis structures that considers the overlapping of orbitals to create bonds. The valence bond theory is only limited in its use because it does not explain the molecular geometry of molecules very well. This is where hybridization and the molecular orbital theory comes into place Dr Seemal Jelani Chem-160 2/27/2019

Hybridization It is a simple model that deals with mixing orbitals to from new, hybridized, orbitals. This is part of the valence bond theory and helps explain bonds formed, the length of bonds, and bond energies; however, this does not explain molecular geometry very well. Dr Seemal Jelani Chem-160 2/27/2019

sp An example of this is acetylene (C2H2) sp  An example of this is acetylene (C2H2). This combines one s orbital with one p orbital. This means that the s and p characteristics are equal. sp2 An example of this is ethylene (C2H4). This is the combination of one s orbital and two p orbitals.  sp3 An example of this is methane (CH4). This is the combination of one s orbital and three p orbitals. Dr Seemal Jelani Chem-160 2/27/2019

Antibonding vs. Bonding Orbitals Electrons that spend most of their time between the nuclei of two atoms are placed into the bonding orbitals Electrons that spend most of their time outside the nuclei of two atoms are placed into antibonding orbitals. Reason This is because there is an increasing in electron density between the nuclei in bonding orbitals, and a decreasing in electron density in antibonding orbitals Placing an electron in the bonding orbital stabilizes the molecule because it is in between the two nuclei Dr Seemal Jelani Chem-160 2/27/2019

Electrons will fill according to the energy levels of the orbitals. Conversely, placing electrons into the antibonding orbitals will decrease the stability of the molecule. Electrons will fill according to the energy levels of the orbitals. They will first fill the lower energy orbitals, and then they will fill the higher energy orbitals. If a bond order of zero is obtained, that means that the molecule is too unstable and so it will not exist. Dr Seemal Jelani Chem-160 2/27/2019

Bonding and non-bonding orbitals of Hydrogen Dr Seemal Jelani Chem-160 2/27/2019

Oxygen Example (homonuclear): Homonuclear species, are molecules composed of only one type of element Dr Seemal Jelani Chem-160 2/27/2019

Type equation here. Dr Seemal Jelani Chem-160 2/27/2019