The number of protons and neutrons left in `""_(92)U^(238)` after emission of an a-particle are

Options

A. 92, 146
B. 90, 144
C. 90, 234
D. 92, 144

Explanation

To find the number of protons and neutrons left in Uranium-238 (U-238) after the emission of an alpha particle, we can follow these steps:

### Step 1: Understand the Composition of U-238
Uranium-238 has:
- Atomic number (Z) = 92 (which means it has 92 protons)
- Mass number (A) = 238 (which means it has a total of 238 nucleons, which are protons and neutrons combined)

### Step 2: Identify the Alpha Particle
An alpha particle consists of:
- 2 protons
- 2 neutrons
- Mass number = 4
- Atomic number = 2

### Step 3: Write the Nuclear Reaction
When U-238 emits an alpha particle, the reaction can be represented as:
\[ _{92}^{238}\text{U} \rightarrow \, _{90}^{234}\text{X} + \, _{2}^{4}\alpha \]
Where X is the new element formed after the alpha emission.

### Step 4: Calculate the New Atomic Number and Mass Number
After the emission of the alpha particle:
- The new atomic number (Z) = 92 - 2 = 90
- The new mass number (A) = 238 - 4 = 234

### Step 5: Determine the Number of Protons and Neutrons in the New Element
- Number of protons in X = 90 (from the new atomic number)
- Number of neutrons in X = Mass number - Number of protons = 234 - 90 = 144

### Final Answer
After the emission of an alpha particle, the number of protons left is 90, and the number of neutrons left is 144.

### Summary
- Protons left: 90
- Neutrons left: 144

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