An element of nucleon number P and atomic number Q emits an alpha particle from its nucleus. The resultant numbers of the new element formed are respectively

vindan

5 months ago

The correct answer is **B. P - 4 and Q - 2**.

To understand why, we need to look at what happens inside the nucleus during alpha decay.

### The Science of Alpha Decay

An **alpha particle** () is essentially a helium nucleus. It consists of **2 protons** and **2 neutrons**. When a radioactive nucleus emits an alpha particle, it is losing these four particles from its core.

* **Nucleon Number (Mass Number, P):** This represents the total number of protons and neutrons. Since the nucleus loses 4 nucleons (2 protons + 2 neutrons), the new mass number becomes ****.
* **Atomic Number (Proton Number, Q):** This represents the number of protons. Since the nucleus loses 2 protons, the new atomic number becomes ****.

### The Decay Equation

In nuclear physics notation, the process looks like this:

Where:

* **X** is the parent element.
* **Y** is the new daughter element.
* **** is the alpha particle.

Because the atomic number () changes, the identity of the element actually changes as well, moving two places back on the periodic table.

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