NEET Chemistry: Inner Transition Elements (Lanthanoids and Actinoids) Practice Questions

Correct answer: C — ns²

Lanthanides are characterized by the filling of the 4f orbitals, following the general configuration of the preceding elements (ns²).

Correct answer: D — f-block

The Lanthanides and Actinides are the elements filling the f-orbitals, which correspond to the f-block of the periodic table.

Correct answer: B — f-block elements

The lanthanoid contraction is the gradual decrease in atomic radii observed across the lanthanoid series (f-block elements) due to poor shielding by the filling 4f orbitals.

Correct answer: C — Uranium

Uranium (U) is the most well-known and commonly studied radioactive element among the Actinoids.

Correct answer: A — The magnetic properties are generally complex and depend on the specific element

The magnetic behavior of lanthanoids is complex, often exhibiting both paramagnetic and diamagnetic properties depending on the specific ion and crystal field environment.

Correct answer: A — Atomic radius

Lanthanoid contraction causes a steady decrease in the atomic radii of the elements as the atomic number increases, especially noticeable in the lanthanide series.

Correct answer: A — Lawrencium (Lr)

Lawrencium (Lr) is the last element in the Actinoid series, completing the sequence of the f-block elements.

Correct answer: C — f-orbitals

The chemical properties of the lanthanoids are largely determined by the spatial extension and participation of the 4f orbitals in bonding and magnetic properties. These 4f orbitals are often poorly shielded and relatively diffuse, allowing for unique electronic configurations.

Correct answer: C — 5f¹ to 5f¹⁴

The general filling order within the actinoid series follows the sequential filling of the 5f orbitals, which is the fundamental basis for the structure of the series.

Correct answer: C — Actinium (Ac)

Actinium (Ac) is the first element in the Actinoid series, marking the beginning of the series that includes elements like Thorium, Uranium, etc.

Correct answer: B — The atomic radii decrease slightly due to the lanthanoid contraction.

The lanthanoid contraction is the progressive decrease in atomic and ionic radii across the lanthanoid series. This occurs because the poor shielding effect of the newly filled 4f-orbitals causes the effective nuclear charge experienced by the outer electrons to increase, pulling them closer to the nucleus.

Correct answer: A — Plutonium (Pu)

Actinoids, especially those in the heavier elements, exhibit varied and sometimes higher oxidation states due to the energetic availability of the 5f electrons, which are more diffuse and participate more actively in bonding than d electrons, compared to the lanthanoids. Plutonium (Pu) is often cited for complex bonding capabilities in this series.

Correct answer: D — f-block

The Lanthanoids and Actinoids are the elements found in the f-block (or inner transition elements). They are defined by the partially filled f-orbitals (4f for lanthanoids and 5f for actinides).

Correct answer: C — f-orbitals

The characteristic feature of the f-block elements (Lanthanoids and Actinoids) is the filling of the subshell orbitals denoted by 'f'.

Correct answer: B — Plutonium (Pu)

The actinoid series begins with the element Uranium (U), which has atomic number 92. While Neptunium (Np) and Plutonium (Pu) are actinides, Uranium is the starting point of the actinoid series.