Final answer:
When the nucleus 22789ac undergoes alpha decay, it loses an alpha particle, resulting in a new nucleus with a mass number of 223 and an atomic number of 87, known as 22387Fr Francium.
Step-by-step explanation:
The question pertains to the process of alpha decay in which a nucleus emits an alpha particle, essentially a helium-4 nucleus. When a nucleus undergoes alpha decay, its mass number decreases by 4 and the atomic number decreases by 2. Given that the parent nucleus is 22789ac, the resulting nucleus after the alpha decay will have a mass number of (227 - 4 = 223) and an atomic number of (89 - 2 = 87). Therefore, the resulting nucleus will be 22387Fr (Francium).
Alpha decay commonly occurs in heavy nuclei with atomic numbers greater than 83, which are too heavy to be stable. The emission of an alpha particle helps such nuclei move closer to the band of stability.