Periodic Properties

JAIDEV EDUCATION SOCIETY

  • Institute Details: J D College of Engineering and Management, Katol Road, Nagpur

    • Website: www.jdcoem.ac.in

    • Email: info@jdcoem.ac.in

    • Type: Autonomous Institute, NAAC "A" Grade

Vision and Mission

  • Vision: Establish a robust foundation for the institute's excellence.

    • Achieving academic excellence through rigorous teaching, learning, and evaluation practices.

    • Developing an ability to apply knowledge of basic science and mathematics in engineering.

    • Providing a supportive environment for the betterment of faculty and students.

Faculty

  • Name of Faculty:

    • Dr. Amit N. Gupta

    • Prof. Priyanka D. Trivedi

    • Prof. Pradnya Deoghare

  • Branches: ME (Mechanical Engineering), CE (Civil Engineering), EE (Electrical Engineering), ETC (Electronics and Telecommunication)

  • Subject: Engineering Chemistry

Theories for Classification of Elements

Prout’s Hypothesis

  • Proposed in 1815.

  • Hydrogen regarded as the central element from which other atoms are derived.

Dobereiner’s Triads

  • Introduced in 1829.

  • Classifies elements into groups of three with similar properties; the atomic weight of the middle element is the mean of the others.

Newland’s Octaves

  • Suggested in 1864, known as the Law of Octaves.

  • Elements arranged by increasing atomic masses; every eighth element shares properties with the first.

Lother Meyer’s Atomic Volume Curve

  • Presented in 1869; relates atomic mass and volume.

  • Grouping of elements with similar properties along the curve.

Mendeleev’s Periodic Table

  • Based on the discovery of 63 elements at the time.

  • Proposed that the chemical and physical properties of elements are periodic functions of their atomic masses.

Modern Periodic Table

  • Proposed by Henry Moseley in the early 20th century.

  • Elements arranged by increasing atomic numbers instead of atomic masses.

  • Key characteristics:

    • Structure: 7 periods (horizontal rows) and 18 groups (vertical columns).

    • The difference in atomic numbers of elements in a group is 8, 18, and 32.

    • Elements grouped based on energy shells; periodicity observed due to atomic structure.

    • Representative elements in groups 1, 2, 13-17; transition elements in groups 3-12.

    • Noble gases in group 18; inert due to full valence shells.

    • Alkali metals (group 1), alkaline earth metals (group 2), halogens (group 17), chalcogens (group 16).

Periodic Properties of the Elements

  • Trends: Elements arranged by increasing atomic number exhibit trends in chemical, physical, and atomic properties.

Atomic Radius

  • Difficult to determine with certainty due to electron probability distribution; defined by internuclear distances.

    • Covalent Radius: half the distance between two nuclei of identical atoms.

    • Anionic Radius: half the distance between two ions in an ionic bond.

    • Metallic Radius: half the distance between nuclei of adjacent atoms in a crystal.

  • Trends: Atomic radius decreases across a period due to increased nuclear charge; increases down a group due to additional shells.

Ionization Energy

  • Defined as the energy required to remove an electron from an atom.

  • Increases across a period and decreases down a group. Noble gases require high energy due to stable octet configuration.

Electron Affinity and Electronegativity

  • Electron Affinity: Defined as the energy change when an electron is added to a gaseous atom; can be positive or negative. Trends: Higher negative values indicate stability of anion.

  • Electronegativity: Measure of an atom's ability to attract electrons in a bond; increases left to right and decreases down a group.

Summary of Periodic Trends

  • Oxidation State: Total number of electrons removed or added. Oxidation state increases with loss of electrons, and decreases with gain.

Hard and Soft Acids and Bases (HSAB) Principle

  • Concept by Ralph Pearson for stability of metal complexes. Lewis acids and bases categorized into hard, soft, and borderline types based on their properties:

    • Hard Acids: Small ionic radii, high charge, strongly solvated.

    • Soft Acids: Large ionic radii, low charge, filled orbitals.

    • Hard Bases: Small ionic radii, strong electronegativity.

    • Soft Bases: Larger radii, intermediate electronegativity.