When calcium atoms lose electrons, they form positively charged ions. Each electron lost corresponds to a positive charge on the ion. Calcium typically loses two electrons when it forms an ion.
1. The neutral symbol for a calcium atom is [tex]\( \text{Ca} \)[/tex].
2. When calcium loses one electron, it would have a +1 charge. This would be represented as [tex]\( \text{Ca}^{+} \)[/tex].
3. However, calcium typically loses two electrons. Therefore, the calcium ion loses two negatively charged electrons, resulting in a +2 charge.
The correct symbol representing calcium atoms that have lost two electrons is [tex]\( \text{Ca}^{+2} \)[/tex].
Thus, the answer to the question is:
[tex]\[ \boxed{Ca^{+2}} \][/tex]
