In nuclear chemistry and radioactivity, which of the following statements about alpha (α) particles is false or incorrect?

Introduction / Context:
Alpha particles, beta particles, and gamma rays are three main types of nuclear radiation. Each has different mass, charge, speed, ionizing power, and penetrating power. Understanding these differences is crucial in nuclear chemistry, radiotherapy, and radiation safety. This question focuses on alpha particles and asks you to identify which statement about their properties is false, meaning it contradicts the actual behaviour of alpha radiation.

Given Data / Assumptions:

• The radiation type under discussion is the alpha (α) particle.
• Alpha particles are known to be helium nuclei.
• The options refer to ionizing power, penetrating power, kinetic energy, and their nuclear identity.
• We assume standard comparative descriptions relative to beta and gamma radiation.

Concept / Approach:
An alpha particle is essentially a helium nucleus consisting of two protons and two neutrons, carrying a +2 charge and relatively large mass compared to beta particles and gamma photons. Because of this mass and charge, alpha particles interact strongly with matter, causing very high ionization along a short path. As a result, they lose energy quickly and have low penetrating power: they can be stopped by a sheet of paper or even the outer layer of human skin. They may have high kinetic energy when emitted, and they certainly have high ionizing power, but they do not have high penetrating power. Therefore, any statement claiming high penetrating power for alpha particles is false.

Step-by-Step Solution:
Step 1: Recall the physical nature of alpha particles. Alpha particles are helium nuclei (2 protons + 2 neutrons) with a +2 charge. Step 2: Examine ionizing power. Due to their large mass and charge, alpha particles cause intense ionization in a short distance; they have high ionizing power. Step 3: Examine penetrating power. Because they interact so strongly, they are stopped quickly and therefore have very low penetrating power. Step 4: Examine kinetic energy. Alpha particles are emitted from nuclei with significant kinetic energy, enough to cause damage along their short path. Step 5: Identify the false statement: the claim that alpha particles have high penetrating power directly contradicts the known low penetration of alpha radiation.

Verification / Alternative check:
Comparative tables of nuclear radiations usually list alpha particles as “high ionization, low penetration”, beta particles as “moderate ionization, moderate penetration”, and gamma rays as “low ionization, very high penetration”. Practical demonstrations show that a sheet of paper or a few centimetres of air can stop most alpha particles, while beta particles require aluminium and gamma rays need thick lead or concrete shielding. Medical physics discussions also emphasise that alpha radiation is dangerous if ingested or inhaled, but not very dangerous externally precisely because it cannot penetrate the outer dead layer of skin. All of these observations confirm that high penetrating power is not a property of alpha particles.

Why Other Options Are Wrong (i.e., actually true statements):
Option A (They have high ionizing power): This is true; alpha particles ionize matter very strongly over a short distance. Option C (They have high kinetic energy): Alpha particles are emitted with considerable kinetic energy and can cause severe local damage if they reach living tissue. Option D (They are positively charged helium nuclei): This is the standard definition of an alpha particle.

Common Pitfalls:
Students often confuse ionizing power with penetrating power, incorrectly thinking that a more ionizing radiation must automatically penetrate more deeply. In reality, high ionization means the radiation loses its energy quickly and is stopped in a short distance, which reduces penetration. Remember the rule of thumb: alpha has high ionization but low penetration, beta is in the middle for both, and gamma has low ionization but very high penetration. Keeping this trio comparison in mind helps avoid such conceptual mistakes.

Final Answer:
The false statement is that alpha particles have high penetrating power; in reality, their penetrating power is low.