Which of the following does not take place by `alpha`-decay

Options

A. `._(92)U^(238) rarr ._(90)Th^(234)`
B. `._(90)Th^(232) rarr ._(88)Ra^(238)`
C. `._(88)Ra^(226) rarr ._(86)Rn^(222)`
D. `._(83)Bi^(213) rarr ._(84)Po^(213)`

Explanation

To determine which of the following does not take place by alpha decay, we need to analyze each option provided in the question. Alpha decay is characterized by the emission of an alpha particle, which consists of 2 protons and 2 neutrons, resulting in a decrease of 2 in the atomic number and a decrease of 4 in the mass number of the parent nucleus.

Let's break down the steps:

### Step 1: Analyze the options
1. **Option 1**: The charge changes from +92 to +90. This indicates a loss of 2 protons, which corresponds to alpha decay.
2. **Option 2**: The charge changes from +98 to +96. Again, this indicates a loss of 2 protons, which corresponds to alpha decay.
3. **Option 3**: The charge changes from +88 to +86. This also indicates a loss of 2 protons, which corresponds to alpha decay.
4. **Option 4**: The charge changes from +83 to +84. Here, the charge increases by 1, which indicates the emission of a beta particle, not an alpha particle.

### Step 2: Identify the correct answer
From the analysis, we see that options 1, 2, and 3 all represent alpha decay as they involve a decrease of 2 in the atomic number. However, option 4 represents a beta decay, where the atomic number increases by 1.

### Conclusion
The correct answer is **Option 4**, as it does not take place by alpha decay.

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