Competency #5
Answer and Explanation
The correct answer is C.
The mass of an electron is very small compared to the mass of the protons and neutrons. In fact, the mass of an electron is about 1800 times smaller than a proton or neutron.
An ion is formed by changing the number of electrons. This does not involve the nucleus, so the numbers of protons and neutrons remain the same. Taking away 2 electrons means the mass is very slightly decreased, but this is decrease is insignificant.
Thus, the mass of any ion is approximately the same as the mass of the neutral atom (from which the ion was formed).
Answer D makes no physical sense; you can never have a negative mass. The charge on the ion is negative, but not the mass.
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