Answer :

When a calcium (Ca) atom forms an ion by losing two electrons, we need to consider the following points:

1. Ion Type: When an atom loses electrons, it becomes a positively charged ion. This type of ion is called a cation.

2. Charge: The charge on the ion depends on the number of electrons lost:
- Calcium originally has 20 protons and 20 electrons.
- By losing two electrons, it has 20 protons but only 18 electrons remaining.
- This results in a net charge of +2 because there are two more protons than electrons.

Therefore, the ion formed by the calcium atom is a cation with a 2+ charge. The correct answer is:

- cation, 2+