Final answer:
The atomic number of the new atom after the francium-223 undergoes beta decay is 88, and the symbol for the new element is Ra, which stands for Radium.
Step-by-step explanation:
The provided nuclear equation represents a beta decay process where a francium-223 atom (with atomic number 87) emits an electron (also known as a beta particle). In beta decay, a neutron in the nucleus is transformed into a proton and an electron. The electron is ejected from the nucleus, represented in the equation as '-1 e'. The atomic number of the new atom (Z) increases by 1 as a result of the newly formed proton, but the mass number (A) remains the same because the total number of protons and neutrons is conserved.
In this case, after the emission of the beta particle, the atomic number increases from 87 to 88. Therefore, the atomic number of the new atom is Z=88. By referencing the periodic table, we can determine that the symbol for the element with atomic number 88 is Ra, which stands for Radium. Thus, the symbol of the new atom is X=Ra.