ATOMIC STRUCTURE CHEMISTRY (diploma 1st semester)

 

Philosophy of Atom by Acharya Kanad

Acharya Kanad proposed that the invisible and indestructible particles called “Parmanu”, or atoms are the basic building blocks of matter.

Definition of Atom

An atom is the smallest unit of an element, consisting of protons, neutrons, and electrons.

Fundamental Particles of Atom

Protons: Positively charged, located in the nucleus.

Neutrons: No charge, located in the nucleus.

Electrons: Negatively charged, located in orbitals around the nucleus.

Atomic Number and Mass Number

Atomic Number (Z): Number of protons in the nucleus.

Mass Number (A): Sum of protons and neutrons in the nucleus.

Isotopes and Isobars

Isotopes: Atoms with the same atomic number but different mass numbers.

Isobars: Atoms with different atomic numbers but the same mass number.

Bohr’s Theory

Proposed by Niels Bohr, it suggests that electrons move in fixed orbits around the nucleus with quantized energies.

Orbitals

Definition: A region of space around the nucleus where an electron is likely to be found.

Shape: Can be spherical (s), dumbbell-shaped (p), cloverleaf-shaped (d), or complex (f).

Orbits vs. Orbitals: Orbits are fixed paths for electrons, while orbitals are regions with a high probability of finding an electron.

Hund’s Rule, Aufbau’s Principle, Pauli’s Exclusion Principle

Hund’s Rule: Electrons fill degenerate orbitals singly before pairing up.

Aufbau’s Principle: Electrons fill orbitals starting from the lowest energy level.

Pauli’s Exclusion Principle: No two electrons in an atom can have the same set of four quantum numbers.

Electronic Configuration (up to atomic no. 30)

The arrangement of electrons in orbitals, subshells, and shells within an atom. For example, the electronic configuration of Zinc (Zn) is [Ar] 3d10 4s2.

Quantum Numbers

Set of numbers that describe the position and energy of an electron in an atom, including principal, azimuthal, magnetic, and spin quantum numbers.

Types of Compounds

Molecular Compounds: Held together by covalent bonds.

Salts: Held together by ionic bonds.

Distinction between Electrovalent and Covalent Compounds

Electrovalent Compounds: Formed by the transfer of electrons, high melting and boiling points, conduct electricity when molten or dissolved in water.

Covalent Compounds: Formed by the sharing of electrons, lower melting and boiling points, do not conduct electricity.

Chemical Bonds

Electrovalent Bond: Formed by the transfer of electrons.

Covalent Bond: Formed by the sharing of electrons.

Coordinate Bond: Formed by the donation of a pair of electrons from one atom to another.

Hydrogen Bond: A weak bond between two molecules resulting from an electrostatic attraction.

Metallic Bond: The attraction between metal ions and delocalized electrons.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory predicts the geometry of molecules based on the repulsion between electron pairs in the valence shell of atoms.

This summary provides a concise overview of atomic structure, touching on key concepts and principles. For a more in-depth study, each topic can be expanded with additional details and examples.