Question

what is the next atomic orbital in the series 1s, 2s, 2p, 3s, 3p?
4s
2d
3f
3d

Explanation:

Based on the Aufbau principle which governs the filling of atomic orbitals in order of increasing energy. After \(3p\), the next orbital with lower energy is \(4s\) (as per the \(n + l\) rule where for \(4s\), \(n + l=4 + 0 = 4\) and for \(3d\), \(n + l=3+2 = 5\), lower \(n + l\) value means lower energy). Also, \(2d\) and \(3f\) do not exist as for \(n = 2\), \(l\) can be \(0\) or \(1\) (no \(d\) - orbital, \(l = 2\) for \(d\) - orbital) and for \(n=3\), \(l\) can be \(0\), \(1\) or \(2\) (no \(f\) - orbital, \(l = 3\) for \(f\) - orbital).

Answer:

4s