Isotope(s) of hydrogen which emits low energy beta- particles with t_1/2 value 12 years is/are
(a)

Q: Why is Tritium radioactive while Deuterium is not?

Radioactivity is often driven by the neutron-to-proton ratio. Deuterium has a ratio of 1:1, which is highly stable for light elements. Tritium has a ratio of 2:1, which creates instability in the nucleus, prompting it to decay to achieve a more stable state.

Q: What exactly is a beta-minus ($\beta^-$) particle?

A beta-minus particle is simply a high-energy, high-speed electron emitted from the nucleus. It is created when a neutron transforms into a proton and an electron to improve the nucleus's stability.

Q: Does Tritium emit harmful radiation?

Tritium emits *low-energy* beta particles. These particles have very low penetration power and cannot even penetrate the dead outer layer of human skin. However, it can be a radiation hazard if inhaled or ingested.

Q: How is Tritium produced if it decays over time?

Tritium is produced naturally in the upper atmosphere when cosmic rays interact with nitrogen molecules. It is also produced artificially in nuclear reactors.

Q: Why doesn't the atomic mass change significantly during beta decay?

During beta decay, a neutron turns into a proton. Since both have approximately the same mass (1 atomic mass unit), the total mass number of the nucleus remains unchanged, even though the atomic number increases by one.

Question

Isotope(s) of hydrogen which emits low energy $\beta^-$ particles with $t_{1/2}$ value > 12 years is/are

Options:

(A) protium

(B) tritium

(C) deuterium

(D) deuterium and tritium

Sigma Percentile · Accepted Answer

Have you ever wondered what makes an element radioactive? It all comes down to a delicate balancing act inside the nucleus. Today, we are going to explore the fascinating world of hydrogen isotopes and uncover the secrets of their stability.

### The Three Flavors of Hydrogen

Imagine you are looking at the fundamental building blocks of the universe. Hydrogen, the simplest element, actually comes in three different flavors, or isotopes.

These are Protium, Deuterium, and Tritium.

While they all share the same number of protons—exactly one—they differ in their neutron count. Protium has zero neutrons, Deuterium has one, and Tritium has two.

This difference in neutrons is the key to their distinct personalities.

### The Quest for Stability

Look closely at Protium and Deuterium.

Because their neutron-to-proton ratio is low, they are perfectly happy and stable. They don't decay.

$$ \frac{n}{p} 	ext{ for Protium} = 0 $$

$$ \frac{n}{p} 	ext{ for Deuterium} = 1 $$

Now, shift your focus to Tritium. It has one proton but two neutrons!

This makes its nucleus quite crowded with neutrons. The neutron-to-proton ratio here is two.

$$ \frac{n}{p} 	ext{ for Tritium} = 2 $$

This imbalance makes the nucleus highly unstable. What happens when a nucleus is unstable? It wants to achieve stability. To do this, it undergoes radioactive decay.

This makes **Tritium the only radioactive isotope** among the three.

### The Beta Decay Mechanism

To fix this imbalance, one of the excess neutrons in Tritium transforms into a proton.

In this process, it spits out an electron to conserve charge.

$$ ^1_0	ext{n} ightarrow ^1_1	ext{p} + ^0_{-1}	ext{e} + \bar{
u}_e $$

This high-speed electron is what we call a **beta-minus ($\beta^-$) particle**. Tritium emits these low-energy beta particles as it slowly transitions into a more stable state.

### The Half-Life Clue

Now, how fast does this happen?

The decay of Tritium is relatively slow. Its half-life, which is the time it takes for half of a sample to decay, is about **12.33 years**.

Notice how this perfectly satisfies the condition in our question, which asks for a half-life greater than 12 years.

Therefore, the isotope that emits low-energy beta particles and has a half-life greater than 12 years is indeed Tritium.

### The Final Transformation

Before we wrap up, let's think about the way forward. What does Tritium actually become after it emits that beta particle?

Since a neutron turned into a proton, the atomic number increases by one, but the mass remains the same.

$$ ^3_1	ext{H} ightarrow ^3_2	ext{He} + \beta^- $$

It becomes **Helium-3**!

Always think about the final products in nuclear reactions. Understanding the *why* behind the decay makes these concepts unforgettable.

Animated Solution for Chemistry - s and p-Block Elements: Isotope(s) of hydrogen which emits low energy $β^{-}$ particles with $t_{1/2}$ value > 12 years is/are

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