I need help with this because it's easy for you guys but I don't understand it

Which of these conditions most likely produces an unstable isotope?

Me i dont know what to do! the table compares the number of electrons in two unknown neutral atoms. comparison of electrons atom number of electrons a 10 d 11 use this information to determine the number of valence electrons in the atoms. which of the following correctly compares the stability of the two atoms? both are unreactive. both are highly reactive. a is unreactive and d is reactive. a is reactive and d is unreactive.

If i had 2 m naoh solution, what does the 2 m stand for? 2 molar, but 2 of a solute in 1