Answer
Balanced nuclear equation:
$^{225}_{90}Th -- \gt ^{221}_{88}Ra + ^4_2He$
Work Step by Step
1. Identify the reaction.
- In an $\alpha$ decay, the initial atom emits a particle with 2 neutrons and 2 protons $(_2^4He)$.
2. Determine the atomic number for : $Th$, and write its complete symbol.
- It is 90. Therefore, the symbol for Th-225 is: $^{225}_{90}Th$.
3. Now, subtract 4 from the mass number, and 2 from the atomic number:
$^{225}_{90}Th --\gt ^{221}_{88}?$
4. Identify the symbol for the element with atomic number equal to 88.
- It is "Ra". So, the main product of that reaction will be: $^{221}_{88}Ra$
5. Write the complete equation:
$^{225}_{90}Th -- \gt ^{221}_{88}Ra + ^4_2He$
