A graph of ( IE _n) versus the number of electrons removed ( n ) is plotted for an unknown element belonging to period 3 of the periodic table. The graph shows a moderate positive slope from n=1 to n=2 , a sudden sharp vertical spike between n=2 and n=3 , and a moderate slope thereafter. Based on this observation, identify the element.

Step-by-step solution

The sudden sharp vertical spike in the ( IE _n) versus n graph between n=2 and n=3 indicates that a very large amount of energy is required to remove the third electron. This implies that the third electron is being removed from a stable, fully-filled noble gas core. Therefore, the element has exactly 2 valence electrons. An element with 2 valence electrons belongs to Group 2 of the periodic table. The Group 2 element present in period 3 is Magnesium (Mg). Answer: Magnesium (Mg)