A sample of selenium was found to contain gaseous ions whose electron configuration can be expressed in bracket notation as
[Ar]3d104s24p6
The neutral selenium atom has atomic number 34.
(a) Write the complete ground-state electron configuration of a neutral Se atom using bracket notation.
(b) Determine the charge on the selenium ion that possesses the configuration shown above. Show your reasoning.
(c) Calculate the total number of valence electrons present in the ion and compare this number with the valence-electron count in the neutral atom. Explain how the change accounts for the stability of the ion produced.
(d) Predict whether the ionic radius of the selenium ion you identified in part (b) is larger than, smaller than, or approximately equal to that of the neutral atom. Justify your prediction in terms of electron–electron repulsions and effective nuclear charge.