Electronic configuration of potassium (#""_19"K")# is

#"1s"^2\ "2s"^2\ color(red)("2p"^6)\ "3s"^2\ "3p"^6\ "4s"^1#

#5^"th", 6^"th"\ &\ 7^"th"# electrons are in #"2p"# subshell. Therefore their principal quantum number (#"n"#) and angular momentum quantum number (#ℓ#) will be #2# and #1# respectively.

Possible magnetic quantum numbers (#"m"_l#) of #"p"#-subshell are #-1, 0, +1#, where #0# is assigned to the #z#.

Spin quantum number (#"m"_s#) of first electron entering in an orbital is #pm1/2#, since they are indistinguishable from the other one in the same orbital.

#underline(bb("Electron" color(white)(...) Orbital color(white)(no..) n color(white)(......) ℓ color(white)(.........) m_l color(white)(..../...) m_s color(white)(...)))#

#color(white)(......)5^"th" color(white)(.............) "2p"_"x" color(white)(............) 2 color(white)(.......) 1 color(white)(.....) -1 color(white)(?.) pm1/2#

#color(white)(......) 6^"th" color(white)(.............) "2p"_"z" color(white)(............) 2 color(white)(.......) 1 color(white)(..........) 0 color(white)(?.) pm1/2#

#color(white)(......) 7^"th" color(white)(.............) "2p"_"y" color(white)(............) 2 color(white)(.......) 1 color(white)(......) +1 color(white)(?.) pm1/2#