Name an atom that loses one electron when it reacts to another atom

Lithium, Sodium, Potassium; any of the Alkali Metals, which are farthest left on the periodic table. This is because they only have one electron in their outermost shell, so they would rather lose an electron rather than try to gain 7 to achieve that full outer shell.

Explanation:

subtract 26.4g-15.4g