Final answer:
The nuclear equation _190^78Pt → _2^4He + ___ represents an alpha decay, where an alpha particle is emitted from Platinum-190. After balancing the mass and atomic numbers, the missing daughter isotope is Osmium-186.
Step-by-step explanation:
The equation that needs to be completed is representing a nuclear reaction, and the type of reaction is alpha decay. In this process, a parent nucleus emits an alpha particle which consists of 2 protons and 2 neutrons (essentially a Helium-4 nucleus). The question asks for the missing daughter isotope given the alpha emission from a parent isotope. The procedure to complete the equation involves balancing the mass and atomic numbers:
Parent isotope: _190^78Pt
Alpha particle: _2^4He
Daughter isotope: _X^Y?
To determine the daughter isotope:
- Subtract the mass number of the alpha particle (4) from the mass number of the parent isotope (190): 190 - 4 = 186.
- Subtract the atomic number of the alpha particle (2) from the atomic number of the parent isotope (78): 78 - 2 = 76.
The element with the atomic number 76 is Osmium (Os). Therefore, the completed equation is:
_190^78Pt → _2^4He + _186^76Os
This demonstrates an alpha decay reaction resulting in Osmium-186.