Problem 20 - A Complete Resource Book in Chemistry for JEE Main

Question

The transition metal with least atomic number is (a) Os (b) \(\mathrm{Zr}\) (c) \(\mathrm{Pt}\) (d) \(\mathrm{Ru}\)

Step-by-Step Solution

Answer

The transition metal with the least atomic number is Zirconium (Zr).

Step 1: Understand the Question

The question asks for the transition metal with the smallest atomic number among the given options: Os, Zr, Pt, and Ru.

Step 2: Recall the Definition

Transition metals are elements found in the d-block of the periodic table, which includes groups 3-12. These metals typically have partially filled d-orbitals.

Step 3: Identify Atomic Numbers

Find the atomic numbers of each element: - Osmium (Os) has atomic number 76. - Zirconium (Zr) has atomic number 40. - Platinum (Pt) has atomic number 78. - Ruthenium (Ru) has atomic number 44.

Step 4: Compare Atomic Numbers

Compare the atomic numbers of the elements to find the smallest: - Zr: 40 - Ru: 44 - Os: 76 - Pt: 78 The smallest atomic number is 40, corresponding to Zirconium (Zr).

Step 5: Conclusion

Based on the atomic numbers, Zirconium (Zr) is the transition metal with the least atomic number among the given options.

Key Concepts

Atomic Number

The atomic number of an element is the number of protons present in the nucleus of its atoms. It is a unique identifier for each chemical element and is typically denoted by the symbol \(Z\). The atomic number determines an element's position on the periodic table and its chemical properties.

• The atomic number directly determines the identity of the element. For instance, all atoms with an atomic number of 6 are carbon atoms.
• It also indicates how many electrons are typically present in a neutral atom of the element, since protons and electrons are equal in a neutral state.
• A higher atomic number means more protons and electrons, leading generally to heavier and more complex atoms.

Understanding atomic numbers allows us to compare and categorize elements, as seen in the exercise determining which transition metal has the smallest atomic number. In our example, among Osmium, Zirconium, Platinum, and Ruthenium, Zirconium, with atomic number 40, is the metal with the fewest protons in its atomic structure.

d-block Elements

The d-block elements, also known as transition metals, occupy groups 3-12 on the periodic table. These elements are characterized by an outermost d-subshell that is progressively filled with electrons.

• The d-block elements typically have partially filled d-orbitals, which contribute to their unique chemical properties, such as forming colored compounds and having multiple oxidation states.
• These elements are often used in various industrial processes due to their ability to act as catalysts and their conductive properties.
• Examples of d-block elements include Iron (Fe), Nickel (Ni), and Copper (Cu), each with distinct uses in electronics, construction, and jewelry.

In the exercise, we examined Osmium (Os), Zirconium (Zr), Platinum (Pt), and Ruthenium (Ru), each of which belongs to the d-block, highlighting their position in these critical groups of transition metals.

Periodic Table

The periodic table is a tabular arrangement of chemical elements ordered by their atomic number, electron configurations, and recurring chemical properties. It was developed to map out elements based on their atomic structure and to predict their chemical behavior.

• Elements in the same column (group) typically have similar properties and the same number of electrons in their outer shell, making the periodic table an insightful tool for chemists.
• The table is divided into blocks corresponding to different subshells (s, p, d, f) being filled, allowing us to understand elements' electron configurations intuitively.
• The transition metals are distinguished by their placement in the d-block, spanning across groups 3 to 12.

The periodic table serves as the foundational framework for all of chemistry. By locating elements such as Osmium, Zirconium, Platinum, and Ruthenium on the table, we can easily ascertain their properties and relationships based on their atomic numbers and positions within the d-block.