Chemistry - PERIODIC TABLE Question with Solution | TestHub

As effective nuclear charge is 2.60 and valence shell contain 3 electrons so the minimum number of main shells for the given element are two i.e., (n = 2) and its configuration will be$1{\mathrm{s}}^2,2{\mathrm{s}}^2,2{\mathrm{p}}^1$.

Hence the given element has 5 electrons in all.

Also, for a neutral atom.

As number of electrons = atomic number = 5.

Thus, the atomic number of the element is 5.