Question

Direction for Assertion - Reason type questions (A) If both Assertion and Reason are true and reason is the correct explanation of assertion. (B) If both Assertion and Reason are true but Reason is not the correct explanation of assertion. (C) If Assertion is true but Reason is false (D) If both assertion and reason are false A: The ionization energy of isolated phosphorous is very large \(\mathrm{R}\) : The ionization energy of phosphorous in lattice is very small (A) a (B) \(b\) (C) \(\mathrm{c}\) (D) \(\mathrm{d}\)

Short answer

The correct answer is (C). The ionization energy of isolated phosphorous is very large, while the ionization energy of phosphorous in lattice is not necessarily 'very small'.

Step-by-step solution

Understand the Terms

Firstly, it is important to comprehend the terms being used. 'Ionization energy' is the energy required to remove an electron from an atom or ion. 'Isolated' phosphorous refers to an individual atom of phosphorous, without any connection to other atoms. 'In lattice' refers to phosphorous as part of a crystal structure where it is bonded with other atoms.

Assess the Assertion

The assertion is: 'The ionization energy of isolated phosphorous is very large.' The isolation energy is typically large for phosphorous. This is because when an atom is isolated, removing an electron would significantly disrupt its stability, requiring a large energy input. So this statement is true.

Assess the Reason

The reason is: 'The ionization energy of phosphorous in lattice is very small.' When phosphorous is in a lattice, it is bonded to other atoms and has lower energy than when it is isolated, making it easier to ionize. However, the statement is not entirely accurate. Even though the energy is lower compared to the isolated state, it might not be right to say that it is 'very small'. So this statement is not necessarily always true.

Analyse the Relationship and Choose the Correct Answer

Since the Assertion is true and the Reason is not entirely true, the best answer would be (C), Assertion is true but Reason is false. While the ionization energy for phosphorous in lattice is smaller than isolated phosphorous, it's not accurate to definitively define it as 'very small'. As these statements are directly linked, the Reason does not correctly explain the Assertion. Thus, the correct answer is (C).

Key concepts

Ionization energy

"Ionization energy" is a crucial concept in chemistry, representing the amount of energy needed to remove an electron from an atom or ion. This process transforms a neutral atom into a positively charged ion. The ionization energy is indicative of an atom's stability; the more stable an atom, the higher the ionization energy.
This energy varies across the periodic table, generally increasing as you move from left to right across a period, due to the increase in nuclear charge which pulls electrons closer to the nucleus, making them harder to remove. Conversely, it decreases as you move down a group because the added electron shells create more shielding, making it easier for outer electrons to be removed.
Understanding ionization energy is important for predicting an element's chemical properties and reactivity. Atoms with high ionization energy, like noble gases, are typically less reactive. Low ionization energy elements, such as the alkali metals, are more eager to lose their outer electrons and engage in chemical reactions.

Phosphorus

"Phosphorus" is a fascinating element with a vital role in various chemical processes. Found in group 15 of the periodic table, it hosts unique properties that contribute to its varied applications, from fertilizers to industrial chemicals.
In its isolated state, phosphorus has a relatively high ionization energy compared to some other groups. This means that a considerable amount of energy is required to remove an electron from a neutral phosphorus atom.
Phosphorus forms several allotropes, with white phosphorus and red phosphorus being the most common. These allotropes display significant differences in their properties; for example, white phosphorus is highly reactive and less stable due to its structure, whereas red phosphorus is more stable and less reactive.
Its versatility in forming compounds is essential, not only in sustaining life via biological systems, such as DNA and ATP but also in various chemical industries.

Chemical bonding

"Chemical bonding" refers to the process where atoms combine to form molecules or compounds through sharing or transferring electrons. It is the force that holds atoms together within a compound, giving rise to the structure and properties of matter.
There are three primary types of chemical bonds: ionic, covalent, and metallic. Each type involves different interactions between the participating atoms.

• Ionic bonding occurs when electrons are transferred between atoms, leading to the formation of oppositely charged ions that attract each other. This is typical of interactions between metals and nonmetals.
• Covalent bonding involves the sharing of electron pairs between atoms, which usually occurs between nonmetals. The shared electrons allow each atom to reach a more stable electron configuration.
• Metallic bonding is a type of bonding typical in metals, where electrons are free to move throughout the structure, providing high conductivity and malleability.

Understanding chemical bonding is key to comprehending how molecules form and react, influencing everything from biochemical reactions to material properties.

Lattice structure

"Lattice structure" refers to the regular arrangement of atoms or ions in a crystalline solid. These structures are foundational in determining the physical properties of materials, from their density to thermal and electrical conductivity.
Lattices are categorized based on their geometric configurations, with the most common being cubic, hexagonal, and tetragonal structures. In each of these configurations, the repetitive pattern of atoms or ions creates a stable and uniform matrix.
In the context of phosphorus, when it forms a lattice, it becomes part of a broader network of atoms bonded together. This interconnectedness affects properties like ionization energy, as the energies involved in altering a structure often differ from those needed for isolated atoms.
Lattice structures are crucial in fields like material science and solid-state physics, helping to explain why materials behave the way they do, including their responses to heat, pressure, and other environmental factors.