Question

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

2d
4s
3r
3d

Explanation:

In electron configuration, after filling \(3p\) orbital, the next orbital to be filled is \(4s\) according to the Aufbau principle (filling orbitals in order of increasing energy \(n + l\), where \(n\) is the principal quantum number and \(l\) is the azimuthal quantum number). For \(3p\): \(n=3\), \(l = 1\), \(n + l=4\). For \(4s\): \(n = 4\), \(l=0\), \(n + l = 4\), and orbitals with lower \(n\) value for the same \(n + l\) are filled first. But there is no \(2d\) (since for \(n = 2\), \(l\) can be \(0\) or \(1\) corresponding to \(s\) and \(p\) orbitals only), no \(3f\) (for \(n=3\), \(l\) can be \(0\), \(1\), \(2\) corresponding to \(s\), \(p\), \(d\) orbitals), and \(3d\) has higher energy (\(n + l=5\) for \(3d\): \(n = 3\), \(l=2\)) than \(4s\) (\(n + l = 4\)).

Answer:

4s