Which atom is most likely to form a 3+ ion?

A. Li
B.Kr
C.P
D.Sr
E.Fe

The atom that is most likely to form a 3+ ion is E. Fe (Iron).

To determine which atom is most likely to form a 3+ ion, we need to look at the electronic configuration and the valence electrons of each atom.

A. Lithium (Li) has an electronic configuration of 1s² 2s¹, and only one valence electron. It is more likely to lose one electron to achieve a stable electron configuration of 1s².

B. Krypton (Kr) has an electronic configuration of [Kr] 5s² 4d¹⁰ 5p⁶, with 8 valence electrons in the outermost shell. It is more likely to gain or lose electrons to achieve a stable electron configuration, and it is less likely to lose 3 electrons to form a 3+ ion.

C. Phosphorus (P) has an electronic configuration of [Ne] 3s² 3p³, with 5 valence electrons. It is more likely to gain 3 electrons to fill its outermost shell and achieve a stable electron configuration than to lose 3 electrons.

D. Strontium (Sr) has an electronic configuration of [Kr] 5s², with 2 valence electrons. It is more likely to lose 2 electrons to achieve a stable electron configuration.

E. Iron (Fe) has an electronic configuration of [Ar] 3d⁶ 4s², with 2 valence electrons in the outermost shell. It is more likely to lose 2 electrons to achieve a stable electron configuration.

Comparing these options, the atom most likely to form a 3+ ion is:

D. Sr (Strontium)

Thus, the correct option is D. Sr.