Problem 12 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is the atomic number of a metal? (a) 32 (b) 34 (c) 36 (d) 38

Step-by-Step Solution

Answer

The atomic number of a metal is 38 (d).

Step 1: Understand the Periodic Table

The atomic number is the number of protons in an atom and determines the identity of the element on the periodic table. Metals are located on the left side and in the middle of the periodic table.

Step 2: Identify Atomic Numbers

Given the options: (a) 32, element Germanium (Ge) - a metalloid; (b) 34, element Selenium (Se) - a nonmetal; (c) 36, element Krypton (Kr) - a noble gas; (d) 38, element Strontium (Sr) - a metal.

Step 3: Conclusion

Most metals are situated to the left and include transition metals, alkaline earth metals, and post-transition metals. Among the given atomic numbers, 38 corresponds to Strontium, which is classified as an alkaline earth metal.

Key Concepts

Periodic Table

The periodic table is a systematic arrangement of all known chemical elements organized by their atomic number, electron configuration, and recurring chemical properties. Each element is represented by a symbol and a unique atomic number, which reflects the number of protons in its nucleus.
Elements are presented in a tabular form, with metals located on the left and in the center, while nonmetals and metalloids are found to the right. The organization highlights trends and patterns, making it easier to understand the relationships between the elements.

• Group: Vertical columns in the periodic table where elements have similar properties.
• Period: Horizontal rows where elements have the same number of atomic orbitals.

The periodic table is a vital tool for chemists and anyone who wants to understand basic chemical behavior. It helps identify not just the physical properties but also how elements interact with each other.

Metals

Metals are elements that typically appear on the left side and in the center of the periodic table. They are characterized by their ability to conduct electricity and heat.
They are usually solid at room temperature, with the exception of mercury, and are often malleable and ductile. Metals tend to lose electrons during chemical reactions and form positive ions.

• Common Properties: High conductivity, shiny appearance, malleability, and high melting points.
• Types of Metals: Transition metals, alkaline earth metals, and alkali metals.

Understanding metals is crucial as they play significant roles in everyday applications, from construction materials to wiring and electronics. Knowing the properties of metals aids in selecting the right materials for specific uses.

Alkaline Earth Metals

Alkaline earth metals belong to Group 2 of the periodic table and are a type of metal. These elements include Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium. They are less reactive than alkali metals (Group 1) but are still too reactive to be found free in nature.
Alkaline earth metals are known for:

• Being shiny and silvery-white
• Having two electrons in their outer shell, which they tend to lose, forming divalent cations (+2 charge)
• Reacting with water, though not as vigorously as alkali metals

Strontium, with an atomic number of 38, is an example of an alkaline earth metal and exhibits these typical properties. These elements are essential in various compounds used in industries and biological systems.