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It's 8th grade science

Which of these conditions most likely produces an unstable isotope?

The number at the end of an isotope’s name is the number.

When the ionic compound nabr dissolves in water, br– ions are pulled into solution by the attraction between what two particles? a. the na+ and br– ions b. the na+ ion and the negative end of a water molecule c. the br– ion and the positive end of a water molecule d. the br– ion and the negative end of a water molecule