you find them on a periodic table
The sum of the percentage abundance of these two isotopes of the new synthetic element should be equal to 100. If we let x be the percent abundance of the second isotope, we have the equation,
62 + x = 100
The value of x from the equation is 38.
Be careful on this one! Mass is always conserved, based on the law of conservation of mass. Since their was a change in state, we went from a solid to a gas, so, the weight would be lighter, not the mass.
Same amount of mass.
Here's how you would solve it. The process should be the same for the others.