Classification Of Elements And Periodicity In Properties (LAQs)

Chemistry-1 | 2. Classification of Elements and Periodicity in Properties – LAQs:
Welcome to LAQs in Chapter 2: Classification of Elements and Periodicity in Properties. This page includes the important FAQs for Long Answer Questions. Answers are given in simple English, with a Telugu translation, and formatted in the exam style. This will aid in understanding the material and achieving top marks in your final exams.

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LAQ-1 : What is periodic property? How the following properties vary in a group and a period? Explain (1) Atomic radius (2) Electron gain enthalpy (3) Electro negativity (EN) (4) Ionisation Enthalpy (IE).

Introduction

Periodic properties are characteristics of elements that exhibit predictable trends across the periodic table. This discussion will focus on how atomic radius, electron gain enthalpy, electronegativity (EN), and ionization enthalpy (IE) vary in groups and periods.

Atomic Radius

1. What is it?: The distance from the nucleus to the outermost electron.
2. Variation in a Group: Increases from top to bottom.
   • Reason: Addition of electron shells increases the radius.
3. Variation in a Period: Decreases from left to right.
   • Reason: Increase in nuclear charge pulls electrons closer, reducing the radius.

Electron Gain Enthalpy

1. What is it?: The energy change when an electron is added to an atom.
2. Variation in a Group: Generally decreases from top to bottom.
   • Reason: Larger atomic size reduces nuclear attraction to additional electrons.
3. Variation in a Period: Generally increases from left to right.
   • Reason: Smaller atomic size and greater nuclear charge increase the atom’s affinity for electrons.

Electronegativity (EN)

1. What is it?: The ability of an atom to attract shared electrons in a chemical bond.
2. Variation in a Group: Decreases from top to bottom.
   • Reason: Increased atomic size reduces the effective nuclear pull on shared electrons.
3. Variation in a Period: Increases from left to right.
   • Reason: Increased nuclear charge enhances the atom’s ability to attract electrons.

Ionization Enthalpy (IE)

1. What is it?: The energy required to remove an electron from an isolated gaseous atom.
2. Variation in a Group: Decreases from top to bottom.
   • Reason: Increased atomic size makes it easier to remove an electron.
3. Variation in a Period: Increases from left to right.
   • Reason: Increased nuclear charge strengthens the hold on electrons, requiring more energy for removal.

Summary

Periodic properties are crucial for understanding the behavior of elements in the periodic table. The trends in atomic radius, electron gain enthalpy, electronegativity, and ionization enthalpy across groups and periods reflect the underlying changes in atomic structure and nuclear charge. These properties are instrumental in predicting the chemical and physical properties of elements.

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LAQ-2 : Define IE1and IE2. Why is IE2 > IE1 for a given atom? Discuss the factors that effect IE of an element.

Introduction

Ionization Enthalpy (IE) refers to the energy required to remove an electron from a gaseous atom or ion.

1. First Ionization Enthalpy (IE_1): The energy needed to remove the first electron from a neutral atom.
2. Second Ionization Enthalpy (IE_2): The energy required to remove the second electron after the first one has been removed.

Why IE_2 > IE_1 for a Given Atom

Increased Nuclear Attraction: After the first electron is removed, the effective nuclear charge on the remaining electrons increases. This increased attraction makes it harder to remove the second electron, hence IE_2 is greater than IE_1.

Factors Affecting Ionization Enthalpy

1. Atomic Size: Larger atoms have lower IE due to the greater distance between the nucleus and the outermost electron, reducing nuclear attraction.
2. Nuclear Charge: Higher nuclear charge results in higher IE, as electrons are more strongly attracted to the nucleus.
3. Shielding Effect: Electrons in inner shells shield outer electrons from the full effect of the nuclear charge, reducing IE.
4. Electron Configuration: Atoms with a stable electronic configuration (like noble gases) or half-filled subshells have higher IE due to increased stability.
5. Subshell Penetration: Electrons in orbitals that are closer to the nucleus (like s-orbitals) are held more tightly, resulting in higher IE.

Summary

Ionization Enthalpy is an essential concept in understanding the reactivity of elements. IE_1 and IE_2 reflect the energy needed to remove the first and second electrons, respectively, with IE_2 generally being higher due to increased nuclear attraction. Factors such as atomic size, nuclear charge, shielding effect, electron configuration, and subshell penetration significantly influence an element’s ionization enthalpy. Understanding these factors is key to predicting and explaining the chemical behavior of elements.

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LAQ-3 : Write an essay on s,p,d and f block elements.

Introduction

The periodic table is divided into four blocks based on the electron configuration of elements: the s, p, d, and f blocks. Each block is named after the type of atomic orbital occupied by the valence electrons of the elements.

S-Block Elements

1. Characteristics: S-block elements include the Group 1 (Alkali Metals) and Group 2 (Alkaline Earth Metals). They have one or two electrons in their outermost s orbital.
2. Properties: These elements are highly reactive, with a strong tendency to lose electrons and form cations.
3. Significance: S-block elements play vital roles in biological systems and are widely used in industry, particularly in batteries and alloys.

P-Block Elements

1. Characteristics: P-block elements span Groups 13 to 18, featuring elements with their last electron entering a p orbital.
2. Diversity: This block includes metals, nonmetals, and metalloids, making it the most diverse block.
3. Applications: Elements here are crucial in life processes and industrial applications, including semiconductors, catalysts, and refrigerants.

D-Block Elements (Transition Metals)

1. Characteristics: D-block elements have their valence electrons in a d orbital. They are known as transition metals and include groups 3 to 12.
2. Properties: Noted for their variable oxidation states and ability to form colored compounds, they are often good conductors of heat and electricity.
3. Uses: Widely used in construction, jewelry, and as catalysts in various industrial processes.

F-Block Elements (Lanthanides and Actinides)

1. Characteristics: The f-block consists of lanthanides and actinides, with valence electrons filling f orbitals.
2. Special Features: These elements are characterized by their radioactive properties and rare earth metals.
3. Applications: They have specialized uses in nuclear energy, electronics, and magnetic materials.

Summary

The s, p, d, and f block elements encompass the entire range of the periodic table, each exhibiting unique properties and applications. From the highly reactive s-block to the diverse p-block, the industrially significant d-block, and the radioactive f-block, these elements play crucial roles in both natural and technological realms. Understanding these blocks is fundamental to the study of chemistry and material science.