The four quantum numbers of the valence electron of potassium are

Atomic number of potassium is 19 and hence electronic configuration will be $1{\mathrm{s}}^2,2{\mathrm{s}}^2,2{\mathrm{p}}^6,3{\mathrm{s}}^2,3{\mathrm{p}}^6,4{\mathrm{s}}^1$

Hence for $4s^1$ electron value of Quantum number are

Principal quantum number n = 4

Azimuthal quantum number l = 0

Magnetic quantum number m = 0

Spin quantum number s = +1/2