The electronic configuration of Einsteinium is : (Given atomic number of Einsteinium $$= 99$$)

Einsteinium has atomic number $$Z = 99$$. The closest noble gas preceding it is Radon (Rn) with $$Z = 86$$, so we represent the core as $$[Rn]$$ and calculate $$99 - 86 = 13$$ electrons remaining.

Following Radon, the orbitals fill in the order $$7s \rightarrow 5f \rightarrow 6d \rightarrow 7p$$. In the actinide series (elements 89-103), the general electronic configuration is $$[Rn] 5f^n 6d^0 7s^2$$, though one $$5f$$ electron may occasionally shift to $$6d$$.

Of the 13 electrons beyond the Radon core, two fill the $$7s$$ orbital to give $$7s^2$$, leaving eleven electrons to enter $$5f$$ as $$5f^{11}$$, with $$6d^0$$ remaining empty. Verifying that $$11 + 0 + 2 = 13$$ confirms that the total $$86 + 13 = 99$$ matches Einsteinium’s atomic number.

Therefore, the electronic configuration of Einsteinium is $$[Rn] 5f^{11} 6d^0 7s^2$$. The correct answer is Option 3: $$[Rn]5f^{11}6d^0 7s^2$$.