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

Which of these would be caused by a chemical change? a) the formation of lava. b) sedimantary rock layering over time. c) metamorphic rock forming from igneous. d) metamorphic rock eroding to form sedimentary rock.

Ineed to find the answer of this question because i dont understand it

Describe at least two advantages and two disadvantages of using hydropower as a source of energy.