how many values of ml are allowed for an electron in a 2s subshell?

For an electron in a 2s subshell, only one value of mlm_lml​ is allowed.

Quick Scoop

• The 2s subshell has:
  • Principal quantum number n=2n=2n=2
  • Azimuthal quantum number l=0l=0l=0 (this is what “s” means)
• The magnetic quantum number mlm_lml​ can take integer values from −l-l−l to +l+l+l.
• For l=0l=0l=0, that range is just:
  • ml=0m_l=0ml​=0

So, the 2s subshell has only one orbital , corresponding to a single allowed mlm_lml​ value: 0. Hence, the number of allowed mlm_lml​ values is 1.