Molecular orbitals Flashcards
Instead of VSEPR, what can provide an explanation for more complex molecules?
molecular orbital theory
When do molecular orbitals form?
when atomic orbitals combine
What is the number of molecular orbitals formed equal to?
the number of atomic orbitals that combine
What does the combination if 2 atomic orbitals result in?
the formation of a bonding molecular orbitals and an antibonding orbital
the bonding molecular encompasses both nuclei
what is the basis of bonding between atoms?
the attraction of the positively charged nuclei and the negatively charged electrons in the bonding molecular orbital
how many electrons can each molecular orbitals hold
max 2
describe the bonding molecular orbital in a non-polar covalent bond
symmetrical about the midpoint between two atoms
what do polar covalent bonds result from? and which atom has a greater share of the bonding electrons?
bonding molecular orbitals that are asymmetric about the midpoint between 2 atoms
the atom with the greater value for EN has the greater share of bonding electrons
What is an example of an extreme case of asymmetry in a bond?
ionic compounds, with the bonding molecular orbitals being almost entirely located around just one atom, resulting in the formation of ions
how are sigma bonds molecular orbitals/sigma bonds formed?
(single bond) (whistle greek sign)
end-on overlap of atomic orbitals along the axis of the covalent bonds
how are pi molecular orbitals/pi bonds formed?
(double bond) (pi greek symbol)
form by side-on overlap of parallel orbitals that lie perpendicular to the axis of the covalent bond
what can the electronic configuration of an isolated carbon atom not explain?
what can explain it?
-the number of bonds formed by the carbon atoms in molecules
-hybridisation
What is hybridisation?
the process of mixing atomic orbitals within an atom to generate a set of new atomic orbitals called hybrid orbitals. These hybrid orbitals are degenerate.
Hybridisation bonding in alkanes
-the 2s orbital and the 3 2p orbitals of carbon hybridise to form 4 degenerate sp3 hybrid orbitals
-these adopt a tetrahedral arrangement
-the sp3 hybrid orbitals overlap end-on with other atomic orbitals to form sigma bonds.
hybridisation bonding in alkenes
-the 2s orbital and 2 of the 2p orbitals hybridise to form 3 degenerate sp2 hybrid orbitals
-these adopt a trigonal planar arrangement
-the hybrid sp2 orbitals overlap end-on to form sigma bonds
-the remaining 2p orbitals on each carbon atom of the double bond is unhybridised and lies perpendicular to the axis of the sigma bond
-the unhybridised p orbitals overlap side-on to form pi bonds
