An atom of an element X gains two electrons. The symbol of the ion formed is

Analyze the question An atom of element X gains two electrons. We need the symbol of the ion that forms.

Concept

• An atom is electrically neutral: the number of protons (+) equals the number of electrons (−).
• Electrons carry a negative charge.
• If an atom gains electrons, it has more negative charges than positive ones, so it becomes a negative ion (anion).
• If an atom loses electrons, it becomes a positive ion (cation).
• The size of the charge equals the number of electrons gained or lost.

Solution

1. The atom X starts neutral, with a charge of 0.
2. It gains 2 electrons, which adds 2 × (−1) = −2 to the charge.
3. The new charge is 0 + (−2) = −2.
4. The ion is written as X²⁻.

Checking the options:

• A. X⁺ is a loss of 1 electron.
• B. X²⁺ is a loss of 2 electrons.
• C. X²⁻ is a gain of 2 electrons. ✔
• D. X⁻ is a gain of 1 electron.

Answer: C. X²⁻

Exam tip Remember "GAIN = Negative, LOSE = Positive". A helpful memory aid is "LEO says GER": Lose Electrons = Oxidation, Gain Electrons = Reduction. For example, oxygen gains 2 electrons to form O²⁻, and chlorine gains 1 electron to form Cl⁻. Metals usually lose electrons to form positive ions, and non-metals usually gain them to form negative ions.