Which change occurs when a barium atom loses two electrons?

• A. It becomes a Ba^{2-} ion.
• B. Its atomic number decreases by two.
• C. It becomes a Ba^{2+} ion.
• D. Its mass number increases by two.

Answer: (C)

Verified step by step guidance

1. Understand that when an atom loses electrons, it becomes a positively charged ion called a cation.
2. Recall that the atomic number represents the number of protons in the nucleus and does not change when electrons are lost or gained.
3. Recognize that the mass number is the sum of protons and neutrons and also remains unchanged when electrons are lost or gained.
4. Since a barium atom loses two electrons, it loses two negative charges, resulting in a net charge of +2, forming a Ba^{2+} ion.
5. Therefore, the correct description of the change is that the barium atom becomes a Ba^{2+} ion.