Question: which element is most likely to gain two electrons when it forms an ion?
Answer: 1 Answer. The elements that are most likely to form 2− ions are the group 16 elements. Their atoms have 6 valence electrons, and need 2 more to have a full valence shell of 8 electrons in order to become stable. When they gain 2 electrons in order to have 8 valence electrons, an octet, they gain a 2− charge.