Chemistry: Atomic Structure Quiz

Introduction to Chemistry

• Chemistry studies the properties, composition, and structure of substances, including elements and compounds.
• Focuses on transformations of these substances and the energy changes involved.

Atomic Structure Overview

• According to John Dalton, an atom is the smallest unit of matter participating in chemical reactions.

Fundamental Particles

• Electrons: Discovered by J.J. Thomson in 1897
  • Mass: 9.107 x 10^-31 kg
  • Charge: -1.602 x 10^-19 C
• Protons: Discovered by E. Goldstein in 1836
  • Mass: 1.672 x 10^-27 kg
  • Charge: +1.602 x 10^-19 C
• Neutrons: Discovered by James Chadwick in 1932
  • Mass: 1.675 x 10^-27 kg
  • Charge: Neutral

Types of Particles

• Temporary Particles: Include mesons, neutrinos, antineutrinos, and positrons.
• Composite Particles: Examples include deuteron and alpha particles.

Dalton's Modern Atomic Theory

• All matter consists of indivisible atoms.
• Atoms of a given element are identical in mass and properties.

Rutherford's Atomic Model

• Known as the nuclear model.
• The nucleus contains protons and neutrons.
• Electrons revolve around the nucleus in fixed circular orbits.

Limitations of Rutherford's Model

• According to Maxwell’s theory, revolving electrons should emit electromagnetic radiation, causing them to lose energy and collapse into the nucleus in less than 10^-8 seconds.
• The model lacks explanations for electron arrangement within the atom.

Bohr's Atomic Theory

• Electrons occupy fixed, circular orbits around the nucleus without radiating energy, termed stationary orbits (K, L, M, N…).
• Electrons can transition between energy levels by emitting or absorbing energy: ΔE = E_high - E_low = hν.
• Angular momentum quantized: mvr = nh/2π, where h = Planck's constant.
• Bohr’s model explains atomic stability and the hydrogen line spectrum.

Limitations of Bohr's Model

• Fails to explain the Zeeman Effect (magnetic field impact on atomic spectra).
• Cannot account for the Stark Effect (electric field impact on atomic spectra).
• Violates the Heisenberg Uncertainty Principle.

Nature of Electrons

• Electrons are negatively charged subatomic particles found in the outer regions of atoms, playing a critical role in chemical bonding and reactions.