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Step-by-step Explanation
Step 1: Recognize the Starting Element
An alkaline earth metal belongs to Group 2 (IIA group) of the periodic table. A classic example is radium (Ra), which is radioactive.
Step 2: Effect of Alpha ($\alpha$) Decay on Atomic Number
When a nucleus undergoes alpha ($\alpha$) decay, it emits an alpha particle, which has 2 protons and 2 neutrons. Thus, each alpha decay decreases the atomic number by 2 and the mass number by 4:
If the original atomic number is $Z$, after one $\alpha$ decay, the new atomic number becomes $Z - 2$.
Step 3: Successive Decays Leading to a Stable Daughter Nuclide
Radioactive nuclides like radium typically undergo a series of decays (multiple alpha and beta emissions). Ultimately, for radium and other heavy radioactive isotopes in this series, the stable final product is lead (Pb). Lead (Pb) is located in Group 14 of the periodic table.
Step 4: Conclude the Final Group
Therefore, after all the successive alpha decays, the daughter element (final stable product) is lead, which belongs to Group 14 (IVA group) of the periodic table.
