When the second ionization energy is supplied to an atom, which ion is formed as a result of removing the second electron?

• A. A 2- anion (e.g., O^{2-})
• B. A neutral atom
• C. A 1+ cation (e.g., Na^{+})
• D. A 2+ cation (e.g., Mg^{2+})

Answer: (D)

Verified step by step guidance

1. Understand that ionization energy refers to the energy required to remove an electron from an atom or ion in the gas phase.
2. The first ionization energy removes the first electron, forming a 1+ cation (e.g., Na \^{+}).
3. The second ionization energy removes a second electron from the 1+ cation, resulting in a 2+ cation (e.g., Mg \^{2+}).
4. Recognize that removing electrons always results in positively charged ions (cations), not negatively charged ions (anions) or neutral atoms.
5. Therefore, after supplying the second ionization energy, the ion formed is a 2+ cation.