If uranium `(` mass number 238 and atomic number 92`)` emits an `alpha-`paticle, the produc has mass number and atomic number

Options

A. 236 and 92
B. 234 and 90
C. 238 and 90
D. 236 and 90

Explanation

To solve the problem, we need to determine the mass number and atomic number of the product formed when uranium-238 emits an alpha particle. Here’s the step-by-step solution:

### Step 1: Identify the initial values
- The mass number of uranium (U) is 238.
- The atomic number of uranium (U) is 92.

### Step 2: Understand the alpha particle
- An alpha particle is essentially a helium nucleus, which has:
- Mass number = 4
- Atomic number = 2

### Step 3: Write the decay equation
When uranium emits an alpha particle, the reaction can be represented as:
\[ \text{Uranium-238} \rightarrow \text{X} + \text{Alpha particle} \]
Where:
- X is the product formed after the emission of the alpha particle.

### Step 4: Calculate the new mass number
To find the mass number of the product (X), subtract the mass number of the alpha particle from the mass number of uranium:
\[ \text{Mass number of X} = 238 - 4 = 234 \]

### Step 5: Calculate the new atomic number
To find the atomic number of the product (X), subtract the atomic number of the alpha particle from the atomic number of uranium:
\[ \text{Atomic number of X} = 92 - 2 = 90 \]

### Step 6: Identify the element
The element with atomic number 90 is thorium (Th). Therefore, the product formed after the emission of the alpha particle is thorium-234.

### Final Answer
- The mass number of the product is 234.
- The atomic number of the product is 90.

### Summary
The product formed when uranium-238 emits an alpha particle is thorium-234, with a mass number of 234 and an atomic number of 90.

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