What are the first three quantum numbers for the electrons located in subshell 2s?

The first three quantum numbers for the electrons located in subshell 2 s are:

n = 2 ℓ = 0 mℓ = 0

Explanation:

Each subshell may have 1 or 2 electrons.

The number 2 in the notation 2s is the first quantum number named main quantum number, n, and it identifies the principal energy level.

So, the first quantum number for any of the two electrons in the subshell 2s is 2.

The letter s is shape of the orbital and it is related with the second quantum number, named azimuthal quantum number and identified with the leter ℓ, as per this table:

Shape of the orbital Azimutal quantun number, ℓ

s 0

p 1

d 2

f 3

So, the second quantum number for any electron in 2s subshell is 0.

As for the third quantum number, it is the magnetic quantum number, identified with mℓ.

The magnetic quantum number, mℓ, can have integer values from - ℓ to + ℓ. Since ℓ = 0, the only valid number for mℓ for the subshell 2s is 0.

Summarizing, the first three quantum numbers for the electrons located in subshell 2 s are:

n = 2 ℓ = 0 mℓ = 0