Final answer:
The nuclear reaction 126/50 Sn to 126/51 Sb is an example of beta decay. During beta decay, the mass number stays the same while the atomic number increases by one, thereby changing the element. A half-life is the time required for half of a radioactive isotope to decay.
Step-by-step explanation:
The nuclear reaction 126/50 Sn → 126/51 Sb is an example of beta decay. In this process, an unstable nucleus emits a beta particle (an electron or positron), which results in the transformation of a neutron into a proton or vice versa, changing the element. The mass number remains the same, but the atomic number increases by one. Beta decay is a common radioactive decay process, just like alpha decay and gamma decay, among others.
Let's consider the decay sequence of 220Th to 208Pb, which involves alpha and beta decay steps. Each step emits a specific particle and results in a new element until lead (Pb) is formed. Here's an example of the first step in this sequence involving alpha decay:
220Th → 216Ra + 4He
The term half-life is defined as the time required for half the atoms in a sample of a radioactive isotope to decay. For example, if nobelium-254 (254No) with a half-life of 55 seconds starts with 1.00 x 10-6 grams, after 55 seconds, only 0.50 x 10-6 grams of 254No would remain.