Rutherford and Bohr Atomic Models Quiz

Atomic Models

• Rutherford's atomic model resembles the planetary motion in the solar system, also known as the Planetary Model.
• Niels Bohr's atomic model overcame the limitations of Rutherford's model based on the Quantum Theory.
• The Bohr Model consists of five principles:
  • Electrons are arranged in concentric circular orbits around the nucleus.
  • Electrons occupy only certain stable orbits or shells.
  • Each orbit or shell is associated with a definite fixed amount of energy, also called energy levels.
  • Energy levels increase with distance from the nucleus.
  • Electrons do not lose energy while revolving in a particular orbit.

Discovery of the Neutron

• In 1932, French physicists Frederic and Irene Joliot-Curie bombarded beryllium nuclei with α-particles, releasing unknown radiation.
• The Joliot-Curies initially hypothesized that the radiation was γ-rays.

Historical Development of Atomic Theories

• Ancient Greek philosopher Empedocles believed that all materials are made up of four elements: earth, air, water, and fire.
• Plato adopted Empedocles' theory and coined the term "element" to describe these four substances.
• Aristotle adopted Empedocles' theory and introduced the idea of differentiating elements based on properties.
• Democritus taught the theory of atomism, believing that indivisible and indestructible atoms are the basic components of all matter.

The Greek Concept of 'Atomos'

• Around 440 BC, Leucippus originated the atom concept, which was refined and extended by Democritus.
• The Greek concept of 'atomos' consists of five major points:
  • All matter is composed of atoms, which are bits of matter too small to be seen.
  • There is a void, which is an empty space between atoms.
  • Atoms are completely solid.
  • Atoms are homogeneous, with no internal structure.
  • Atomic Theory is the way to interpret facts about atoms.

Dalton's Atomic Theory

• Dalton studied the weights of various elements and compounds.
• Postulates of Dalton's Atomic Theory:
  • Elements are made of small particles called atoms.
  • Atoms can neither be created nor destroyed.
  • All atoms of the same element are identical and have the same mass and size.
  • Atoms of different elements have different masses and size.
  • Atoms combine in small whole numbers to form compounds.

Modern Atomic Theory

• Drawbacks of Dalton's Atomic Theory:
  • The indivisibility of an atom was proved wrong.
  • Atoms of the same element are similar in all properties was proved wrong.
  • Atoms of different elements differ in mass was proved wrong.
  • Atoms of different elements combine in simple whole-number ratios to form compounds was proved wrong.
• Modern Atomic Theory Postulates:
  • Elements are made of small particles called atoms.
  • Atoms cannot be created or destroyed during ordinary chemical reactions.
  • All atoms of the same element have the same atomic number but may vary in mass number due to the presence of different isotopes.
  • Atoms of different elements are different.