Q.Explain with example α - decay.

Step 1. An alpha particle is a helium-4 nucleus (4-2-He): 2 protons and 2 neutrons bound together, carrying charge +2 and mass 4u.

Step 2. In alpha decay, a parent nucleus $^{A}_{Z}X$ spontaneously ejects one alpha particle, becoming a daughter nucleus $Y$ with mass number 4 less and atomic number 2 less than the parent: $^{A}_{Z}X \rightarrow\ ^{A-4}_{Z-2}Y + 4$-$2$-$He$.

Step 3. Worked example: radium-226 alpha-decays to radon-222, 226-88-Ra → 222-86-Rn + 4-2-He (mass number 226-4=222 checks; atomic number 88-2=86 checks). A second example from this chapter: uranium-238 alpha-decays to thorium-234, 238-92-U → 234-90-Th + 4-2-He. …

State the alpha-particle identity, give the general alpha-decay equation, and illustrate with a worked example from …

• Forgetting alpha decay changes BOTH mass number (by 4) and atomic number (by 2), unlike beta decay which changes only atomic number. …