1. The formula of the ionic compound that forms from two ions, A2+and R5-, can be written as AxRy. What is the value of x?
2. A specific radioactive isotope has a half-life of 39.2 minutes. How long will it take this isotope to decay 1/8 of its original amount?
3. Two short-lived isotopes of an element are produced in a nuclear reaction. One of these isotopes has a mass of 5.3731 amu and accounts for 75.5% of the production. The remaining isotope has a mass of 7.3904 amu. Use this information to calculate the atomic mass of this element.