Answer: The electronic configuration of [Kr] corresponds to the 36 electrons in the closed inner shell of a noble gas. Therefore, the ion with a +2 charge must have lost two electrons from its outermost shell.
To determine the element, we need to find which element has 2 valence electrons and can form a cation with a +2 charge. The element in question is located in Group 2 of the periodic table, which includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
Out of these elements, only magnesium (Mg) has 2 valence electrons and can form a cation with a +2 charge. Therefore, the element in question is magnesium, and the ion with a +2 charge is Mg2+.
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