Final answer:
The combinations of n and l that represent real orbitals are 1s, 4s, and 2p. The combination 2db does not exist.
Step-by-step explanation:
The combinations of n and l that represent real orbitals are:
a. 1s
c. 4s
d. 2p
The combination of n and l that does not exist is:
b. 2db
To understand which combinations of n and l represent real orbitals, we need to understand the quantum numbers n and l. The principal quantum number (n) determines the energy level or the size of the orbital. The azimuthal quantum number (l) determines the shape of the orbital. The value of l ranges from 0 to (n-1), which means that for a given energy level n, the possible values of l are 0, 1, 2, ..., (n-1).
For example, when n = 1, the only possible value of l is 0, so the combination 1s represents a real orbital. When n = 2, the possible values of l are 0 and 1, so the combinations 2s and 2p represent real orbitals. However, the combination 2db, which represents a combination of d and b orbitals, does not exist because there is no d orbital with an azimuthal quantum number of 2.
In summary, the combinations of n and l that represent real orbitals are 1s, 4s, and 2p. The combination 2db does not exist.