Which element possesses a -2 charge when it combines with other elements?  

• A. Ca
• B. Mn
• C. P
• D. Se
• E. F

Answer: (D)

Verified step by step guidance

1. Understand that elements form ions by gaining or losing electrons to achieve a stable electron configuration, often resembling the nearest noble gas.
2. Recall that elements in Group 16 (the chalcogens) typically gain 2 electrons to form ions with a -2 charge because they have 6 valence electrons and need 2 more to complete their octet.
3. Identify the element among the options that belongs to Group 16; Selenium (Se) is in Group 16 and commonly forms a -2 charge ion (Se^{2-}).
4. Recognize that other elements listed, such as Ca (a metal in Group 2), typically form positive ions (Ca^{2+}), and F (a halogen) typically forms a -1 charge ion (F^{-}).
5. Conclude that the element which forms a -2 charge ion when combining with other elements is Selenium (Se).