Answer
There are 2 electron states.
Work Step by Step
$n=2, l=0$
In general, the allowed values of $m_l$ are $~~m_l = 0, \pm 1, \pm 2,...,\pm l$
If $l=0,$ then the allowed value of $m_l$ is $~~m_l = 0$
There is 1 possible value of $m_l$
For each value of $m_l$, there are 2 possible values of $m_s$
The number of electron states is $~~(1)(2) = 2$
In general, for a given $l$, the number of electron states is $~~2(2l+1)$
We can verify the number of electron states we found above:
$2(2l+1) = 2[2(0)+1] = 2$
There are 2 electron states.
