Question

what do all the electron configurations have in common?
all of the obtained electron configurations are isoelectronic with
group 2a elements.
group 6a elements.
noble gases.
group 7a elements.
group 1a elements.

Explanation:

Isoelectronic species have the same number of electrons. Noble gases have completely filled valence shells. Many ions (like \(Na^+\), \(Mg^{2+}\), \(O^{2 -}\), \(F^-\)) achieve stable electron configurations by losing or gaining electrons to become isoelectronic with noble gases. Group 1A elements (except H) lose 1 electron to form \(+1\) ions, group 2A elements lose 2 electrons to form \(+2\) ions, group 6A elements gain 2 electrons to form \(- 2\) ions, group 7A elements gain 1 electron to form \(-1\) ions. These ions often have electron configurations similar to noble gases.

Answer:

noble gases.