How many possible combinations are there for the values of l and ml when n2?

For the principal quantum number ( n = 2 ), the possible values of the azimuthal quantum number ( l ) are 0 and 1 (since ( l ) can take on values from 0 to ( n-1 )). For each value of ( l ), the magnetic quantum number ( m_l ) can take values from (-l) to (+l). Therefore, for ( l = 0 ), ( m_l = 0 ) (1 combination), and for ( l = 1), ( m_l ) can be (-1, 0, +1) (3 combinations). In total, there are ( 1 + 3 = 4 ) possible combinations of ( l ) and ( m_l ) for ( n = 2 ).