Video Transcript
Molecular bonds, the chemical bonds in molecules, are formed from the overlap of
atomic orbitals. Which two atomic orbitals’ overlap is likely to have formed the molecular orbital
shown?
Atomic orbitals are three-dimensional mathematical expressions that describe the most
likely location of an electron in an atom. The diagram shown, however, is for a molecular orbital, and we are told it forms from
the overlap of atomic orbitals. The four most commonly discussed orbitals are s orbitals, p orbitals, d orbitals, and
f orbitals. d and f orbitals have several interesting shapes, and we know that s
orbitals are spherical in shape and p orbitals dumbbell in shape. When atomic orbitals overlap and combine, they form molecular orbitals. Molecular orbitals are mathematical functions that describe the location and wavelike
behavior of electrons in molecules.
There are two general types of molecular orbitals: antibonding molecular orbitals and
bonding molecular orbitals. Bonding molecular orbitals are lower in energy and contribute to a stronger bond. Here is an example of how molecular orbitals form. When the valence s atomic orbitals of two atoms, for example, two hydrogen atoms,
overlap and combine, a 𝜎s antibonding molecular orbital of this shape forms, as
well as 𝜎s bonding molecular orbital. This 𝜎s orbital is the molecular bond between two hydrogen atoms in H2. We are not interested in antibonding molecular orbitals here, so let’s erase
this.
Notice that when s valence orbitals overlap and combine, they produce a bonding
molecular orbital of this shape. However, we are asked about this shape here, which could not have been produced from
the overlap of two s atomic orbitals. When a valence s atomic orbital and a valence p atomic orbital, for example, in an
atom of hydrogen and an atom of fluorine, respectively, overlap and combine, they
form a bonding molecular orbital that looks like this for hydrogen fluoride. And when p valence orbitals, for example, from two fluorine atoms, overlap and
combine head-on, a bonding molecular orbital of this shape is formed for F2, the
diatomic fluorine molecule. Notice that the molecular orbital given in the question has the same shape.
So, which two atomic orbitals’ overlap is likely to have formed the molecular orbital
shown? The answer is p orbitals.
