Isotope one hyphenated name is Br-81. What is the hyphenated name of the
unknown isotope?

Which of the following true? a_volcanoes and earthquakes often near the plate boundaries. b_volcanoes occur whereve there are tall mountains. c_earthquakes cause volcanoes in the same location to erupt violently d_volcanoes and earthquakes occur only where plates are colliding with each other

What happens to isotopes that are unstable?

Ineed ! i have no clue how to do this problem.