Identifying D-Block Elements Associated with Alpha Rays

The question asks us to identify a d-block element from the given options that is represented by the Greek symbol '\(\alpha\)' and metallic 'rays'. The Greek symbol '\(\alpha\)' is universally used to represent an alpha particle. Alpha particles are emitted during a specific type of radioactive decay known as alpha decay. These particles are essentially helium nuclei, consisting of two protons and two neutrons.

Alpha decay is a common mode of radioactive decay for very heavy atomic nuclei. Elements that undergo alpha decay are radioactive and emit these 'alpha rays'. The question connects a d-block element to this phenomenon.

Let's examine the options provided:

• Lanthanum (La): Atomic number 57. While often grouped with the d-block elements in Group 3, it is the first element of the lanthanide series, which are f-block elements. Its most common isotopes are stable, though some radioactive isotopes exist which undergo beta decay or electron capture. It is not primarily known for alpha decay.
• Actinium (Ac): Atomic number 89. Like Lanthanum, Actinium is typically placed in Group 3 and is the first element of the actinide series, which are f-block elements. However, its properties and common periodic table placement often associate it with the d-block. Actinium is a highly radioactive metallic element. The Actinium decay series begins with Uranium-235 and involves Actinium-227 (\(^{227}\)Ac). Many isotopes of Actinium undergo alpha decay, emitting alpha particles (alpha rays). Actinium's strong association with radioactivity and alpha emission makes it a strong candidate.
• Rhenium (Re): Atomic number 75. This is a true d-block element located in Group 7. Rhenium has stable isotopes and some radioactive isotopes. Its radioactive isotopes, such as Rhenium-187 (\(^{187}\)Re), undergo beta decay, not alpha decay.
• Tungsten (W): Atomic number 74. This is also a true d-block element located in Group 6. Tungsten has several stable isotopes. While some very long-lived radioactive isotopes exist (e.g., \(^{180}\)W) that undergo alpha decay, alpha emission is extremely rare for Tungsten and not its defining radioactive characteristic compared to elements in the actinide series.

Considering the association with the Greek symbol '\(\alpha\)' representing alpha rays, we need an element that is radioactive and undergoes significant alpha decay. Among the options, Actinium (Ac) is a highly radioactive element whose decay series involves the emission of alpha particles. Although it initiates the actinide series (f-block), it is traditionally placed in Group 3 alongside d-block elements like Scandium and Yttrium due to electron configuration and chemical similarities.

Therefore, Actinium is the d-block (or d-block associated) element among the choices that is prominently represented by the emission of alpha particles (alpha rays).

Based on the analysis, Actinium is the element that fits the description of being a d-block element (by common grouping) and is strongly associated with alpha particles ('\(\alpha\)') or alpha rays due to its radioactivity and prevalent alpha decay.

Revision Table: Key Concepts

Additional Information on Actinium and Alpha Radiation

Actinium (\(^{227}\)Ac) is a naturally occurring radioactive metal found in trace amounts in uranium ores. It is about 150 times more radioactive than Radium. Its isotopes decay via complex pathways involving both alpha and beta decay. The association of Actinium with the Actinium series, which is characterized by the emission of alpha particles (\(\alpha\)), directly links the element to the Greek symbol '\(\alpha\)' and alpha rays mentioned in the question. Although chemically resembling the lanthanides, Actinium is the first element of the actinide series and shares properties with both Group 3 d-block elements and the subsequent f-block actinides. Its inclusion as a 'd-block' element in this context likely refers to its placement in Group 3.