Question

How many values of m_ℓ are allowed for an electron in a 2s subshell?

And can you explain please? I thought it would be 4.

Answer 1

for a value of "l", the m_l values range from "-l" to "+l"

for s-orbital, l = 0

so m_l value ranges from -0 to +0 i.e., "0"

So for a 2s-subshell only one value is valid