Question

Assume X it a representative element in the periodic table. Which of the following is true if it makes the ion shown below? Multi select.

X 2 +

a
it gains two electrons when it forms ions
b
This ion has the electron configuration of the noble gas coming before this element.
c
it donates two electrons when it forms ions
d
This ion has the electron configuration of the noble gas coming after this element.

Answer 1

Correct answers: b and c.

Explanation:
- X2+ is a 2+ cation, so the atom has lost (donated) two electrons — not gained them (so a is false, c is true).
- Losing the two valence electrons typically leaves the ion with the electron configuration of the noble gas in the previous period (lower atomic number). Example: Mg → Mg2+ has the Ne configuration; Ca2+ has the Ar configuration. Thus b is true and d is false.