What allows sigma bonds to overlap?
1 Answer
Sigma bonds cannot overlap. Sigma orbitals overlap.
Two orbitals can overlap if and only if they have the same "symmetry" AND they have similar energies.
Two orbitals can overlap in a sigma (
You do not have to know what it means for two orbitals to transform under the same symmetry in a General Chemistry class. What you do have to know is that two identical orbitals are always, always compatible.
#s + s# (e.g.#"H"_2# )#s + p_z# (e.g.#"HCl"# )#s + d_(z^2)# (transition metal complex; axial, e.g.#"M"-"H"# bond)#s + d_(x^2-y^2)# (transition metal complex; equatorial, e.g.#"M"-"H"# bond)#p_z + p_z# (e.g.#"Br"_2# )#p_y + d_(z^2)# (polyatomic transition metal complex, where the#y# axis is the axis going from the ligand to the metal); axial, e.g.#"M"-"CN"# bond,#"M"-"OH"# bond, etc.#p_y + d_(x^2-y^2)# (polyatomic transition metal complex, where the#y# axis is the axis going from the ligand to the metal); equatorial, e.g.#"M"-"CN"# bond,#"M"-"OH"# bond, etc.#d_(z^2) + d_(z^2)# (e.g.#(eta^5-"C"_5"H"_5)_2"Zn"_2# , a "sandwich" compound with a#"Zn"-"Zn"# bond sandwiched in between two five-membered aromatic rings); this "sandwiching" is not common.
In General Chemistry, the extent of what you will see is likely (1), (2), and (5). You probably won't see (3) or (4) until you take Inorganic Chemistry (first semester of two), and you probably won't discuss (6), (7), or (8) until second-semester Inorganic Chemistry.
That's most if not all the possible combinations that form a
As long as two atoms bond along the internuclear axis, the first orbital overlap that they make to form a single bond will always be a
