Yes, radioactive decay can reduce an object's mass. Radioactive decay is a natural process in which unstable atomic nuclei undergo spontaneous changes, releasing radiation in the form of particles and/or energy. During radioactive decay, the parent nucleus transforms into a different nucleus, which may have a different number of protons and neutrons.
In certain types of radioactive decay, such as alpha decay and beta decay, particles are emitted from the nucleus. For example, in alpha decay, an alpha particle, which consists of two protons and two neutrons, is emitted from the nucleus. In beta decay, either an electron (beta-minus decay) or a positron (beta-plus decay) is emitted.
When particles are emitted during radioactive decay, they carry away some energy and momentum from the system. According to Einstein's mass-energy equivalence principle (E=mc²), energy and mass are interrelated. The energy carried away by the emitted particles corresponds to a reduction in the mass of the decaying nucleus or the entire object, as per the principle of conservation of mass-energy.
It's important to note that the mass loss due to radioactive decay is generally very small on a macroscopic scale. However, for certain unstable isotopes with long half-lives or in cases of significant radioactive decay over extended periods, the cumulative effect can be measurable. Nonetheless, the overall mass loss from a decaying object is typically negligible for everyday practical purposes.