The new atomic number is 86 and the new mass number is 222.
Work Step by Step
The atomic number decreases by 2 for alpha emission, because alpha particles carry a charge of +2e. The radium atom becomes a radon atom. The mass number decreases by 4 for alpha emission, because alpha particles have 4 nucleons. This is discussed on pages 628-629. The periodic table on page 216 is also helpful.