Thorium is an element that occurs naturally in the earth's crust. The only naturally occurring isotope of thorium is 232Th and i
t is unstable and radioactive. The first step in the Thorium decay chain is the emission of an alpha particle. Which of these nuclei emerges from the decay? A) 22888Ra B) 23086Rn C) 23289Ac D) 23892U
A, radium-228. Alpha radiation is essentially just two protons and two neutrons leaving the atom, causing the atomic number to drop by two (since the protons left) and the mass number to drop by four (since two neutrons and protons left).
In alpha decay a helium nucleus, 42He, is emitted. Since the total number of nucleons must be conserved, the atomic number of the parent nucleus must decrease by two, and the mass number must decrease by four. Here, the new atomic number is 90 - 2 = 88, and new mass number is 232 - 4 = 228.
Explanation:If the mass of the object stays the same but the volume of the object decreases then its density becomes greater. If the volume of the object stays the same but the mass of the object increases then its density becomes greater.
