Effective nuclear charge =2.60 and valence shell contain 3 electrons.
Thus, the minimum number of main shells for the given element are two i.e., (n=2) and its configuration will be 1s2,2s2,2p1.
so that the given element has 5 electrons in all.
Also, for a neutral atom.
therefore, No. of electrons = Atomic number
Thus, the atomic number of the element is 5.
