Lightest transition element is? (a) \(\mathrm{Fe}\) (b) \(\mathrm{Sc}\) (c) Os (d) \(\mathrm{Pd}\)

The periodic table serves as a tabular display of the chemical elements, organized by atomic number, electron configuration, and recurring chemical properties. Elements are presented in order of increasing atomic number, which is the number of protons in an atom's nucleus. The table has rows called periods and columns called groups. Transition elements are positioned in the central part of the table.

Specifically, the lighter transition elements are found in the first few rows of the d-block, which holds the groups 3 to 12. This region is critical for understanding chemical reactivity and bonding in metals. Recognizing the placement of transition metals in the periodic table is essential for predicting their behavior and interactions with other elements.

Atomic weight, also known as relative atomic mass, is a measurement of the mass of an atom. It's a weighted average of the various isotopes of an element as they naturally occur. Each element in the periodic table displays its atomic weight, making it easier to compare the 'heaviness' or 'lightness' of different elements.

The atomic weight is crucial in chemistry for a variety of calculations, including determining the proportions in which elements combine to form compounds, and identifying the lightest or heaviest among a given set of elements. For the transition elements, tracking atomic weights can also inform us about their densities and stabilities, which are important properties in material science and chemistry.

D-block elements, commonly known as transition metals, include elements in groups 3 to 12 of the periodic table. These elements are characterized by the filling of d-orbitals with electrons, which leads to their unique chemical and physical properties such as high melting points, malleability, and the ability to conduct electricity.

The d-block elements form colorful compounds, often exhibit variable oxidation states, and are known for their catalytic activities. They play pivotal roles in biological systems as well as in industrial applications. For example, iron (Fe) is essential in the transport of oxygen in the blood, while catalysts made from palladium (Pd) are used in chemical synthesis. Remembering that these elements are both technically and biologically significant will aid in the understanding of the broader context of their study in chemistry.