Which of the following subshells is correctly designated?

a. 1f5
b. 3s3
c. 6f12
d. 4d11
e. 1p2

a. For n=1, there is no f subshell

b. an s subshell cannot have 3 electrons
e. There is no p subshell in an n=1 shell

That leaves d or f. Consider the maximum number of elctrons each can have and you will have the answer.

To understand the correct designation of the subshells, we need to understand the notation used to represent subshells in electron configuration.

The notation used for subshells consists of two parts: the principal quantum number (n) and the azimuthal quantum number (l). The principal quantum number (n) represents the energy level of an electron, and it can have any positive integer value (1, 2, 3, etc.). The azimuthal quantum number (l) represents the shape of the subshell and depends on the value of n. It can have integer values ranging from 0 to n-1.

Now let's analyze the given options:

a. 1f5
This notation is incorrect because the principal quantum number (n) for the 1s subshell is 1, and the azimuthal quantum number (l) can only be 0 for the s subshell. The letter "f" does not correspond to any valid subshell shape for n = 1.

b. 3s3
This notation is correct. The principal quantum number (n) is 3, and the azimuthal quantum number (l) is 0. The letter "s" represents the shape of the subshell.

c. 6f12
This notation is correct. The principal quantum number (n) is 6, and the azimuthal quantum number (l) is 3. The letter "f" represents the shape of the subshell.

d. 4d11
This notation is correct. The principal quantum number (n) is 4, and the azimuthal quantum number (l) is 2. The letter "d" represents the shape of the subshell.

e. 1p2
This notation is correct. The principal quantum number (n) is 1, and the azimuthal quantum number (l) is 1. The letter "p" represents the shape of the subshell.

Therefore, the correctly designated subshells among the given options are:
b. 3s3
c. 6f12
d. 4d11
e. 1p2