Problem 8 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

he statements that are true for the long form of the periodic table are: (a) it reflects the sequence of filling the electrons in the order of subenergy level \(\mathrm{s}, \mathrm{p}, \mathrm{d}\) and \(\mathrm{f}\). (b) it helps to predict the stable valency states of the elements (c) it reflects trends in physical and chemical properties of the elements (d) it helps to predict the relative ionicity of the bond between any two elements.

Step-by-Step Solution

Answer

All statements (a), (b), (c), and (d) are true.

Step 1: Understand the Statement

We need to review each of the provided statements about the long form of the periodic table to determine which ones are true.

Step 2: Statement (a) Verification

Statement (a) claims that the long form of the periodic table reflects the sequence of filling the electrons in the order of subenergy level \(\mathrm{s}, \mathrm{p}, \mathrm{d}\) and \(\mathrm{f}\). This is true because the periodic table is organized based on the electron configuration of atoms, which fills orbitals in this specific sequence.

Step 3: Statement (b) Verification

Statement (b) suggests that the periodic table helps to predict the stable valency states of the elements. This is correct since the group in the periodic table indicates the number of valence electrons, which helps predict valency.

Step 4: Statement (c) Verification

Statement (c) asserts that the periodic table reflects trends in physical and chemical properties of the elements. This statement is true, as elements in the same group often exhibit similar properties, and trends like electronegativity, atomic radius, and ionization energy are evident.

Step 5: Statement (d) Verification

Statement (d) claims that the periodic table helps to predict the relative ionicity of the bond between any two elements. The periodic table does help with this since differences in electronegativity between elements, which can be inferred from their positions, are a key factor in determining bond ionicity.

Step 6: Conclusion

All four statements (a), (b), (c), and (d) are true regarding the long form of the periodic table.

Key Concepts

Electron Configuration

The concept of electron configuration is crucial to understanding the organization of the periodic table. Electrons in an atom fill orbitals in a specific sequence that is based on their energy levels. This sequence follows the order of the subenergy levels denoted as \(\mathrm{s}, \mathrm{p}, \mathrm{d},\) and \(\mathrm{f}\). These sublevels are distributed among the main energy levels, helping to define the electron arrangement within an atom.
The periodic table is designed to reflect electron configurations. As you move across a period (row), each element adds one more proton and one more electron to its structure. Electrons are filled into orbitals following the rules of the Aufbau principle, which states that electrons fill the lowest energy orbitals first.
Understanding the electron configuration allows you to predict how an element will interact chemically, as it provides insight into the number of valence electrons, essential for forming chemical bonds.

Valency

Valency is a fundamental concept in chemistry, referring to the ability of an element to form bonds with other elements. It is largely determined by the number of electrons in the outer shell, known as valence electrons.
In the long form of the periodic table, group numbers can indicate valency. Elements in the same group typically have the same number of valence electrons and thus similar valency. For example, elements in Group 1 all have one valence electron, making them highly reactive and typically forming bonds by losing this one electron.
Valency helps predict the chemical behavior of elements, such as whether they will form ionic or covalent bonds, their reactivity, and the types of compounds they might form. Understanding valency is crucial in predicting how elements will interact in chemical reactions.

Chemical Properties

The periodic table not only classifies elements but also reflects trends in their chemical properties. Elements within the same group in the periodic table exhibit similar chemical behavior due to having the same number of valence electrons. This consistency leads to patterns known as periodic trends.
Some chemical properties that can be predicted using the periodic table include:

• Reactivity: How readily an element participates in chemical reactions. For example, alkali metals in Group 1 are known for their high reactivity, especially with water.
• Electronegativity: The ability of an atom to attract electrons when forming a bond. This property generally increases across a period and decreases down a group.
• Ionization Energy: The energy required to remove an electron from an atom. Like electronegativity, ionization energy typically increases across a period and decreases down a group.

Recognizing these trends helps in predicting how elements might interact in various chemical contexts.

Ionic Bonds

Ionic bonds are a type of chemical bond formed between two atoms when one atom donates an electron to another. This usually occurs between metals and non-metals, with the metal losing an electron and the non-metal gaining it.
The periodic table aids in predicting ionic bond formation by providing information on electronegativity. When two elements with a significant difference in electronegativity form a bond, it is likely to be ionic. The metal, with lower electronegativity, loses electrons, while the non-metal, with higher electronegativity, gains those electrons.
Some key characteristics of ionic bonds include:

• Formation of ions: Positive cations and negative anions are formed.
• High melting and boiling points: Due to the strong attraction between oppositely charged ions, ionic compounds exhibit high melting and boiling points.
• Electrical Conductivity: Ionic compounds conduct electricity when dissolved in water or molten, as the ions are free to move and carry charge.

Using the periodic table, one can predict the likelihood of ionic bond formation by examining the elements' positions and their respective electronegativities.