Identify the incorrect statement regarding radioactive decay:

Explanation

Option A is incorrect because alpha particle emission causes the element to lose two protons and two neutrons, resulting in a decrease in positive charge, not a gain in negative charge. Option B is also incorrect since beta emission increases the positive charge by converting a neutron into a proton. Option C is false because radioactive decay is exponential; a substance never completely disappears after two half-lives, only about 75% decays. Option D is true because the decay constant is a fixed property unaffected by external conditions like temperature, pressure, or concentration.