Mnemonics: Atoms | Physics Class 12 - NEET PDF Download

Atomic Models

Types: Thomson, Rutherford, Bohr

Mnemonic: "The ​Real Beauty"

Breakdown:

• The - Thomson
  Thomson Model: Also known as the "plum pudding" model, where electrons are spread throughout a positively charged sphere. It was the first model to suggest that atoms are made of smaller particles.
  Example: J.J. Thomson’s cathode ray experiment led to the discovery of the electron.
• Real - Rutherford
  Rutherford Model: Proposed that the atom consists of a dense, positively charged nucleus with electrons orbiting around it, much like planets orbit the sun.
  Example: Rutherford’s gold foil experiment revealed the existence of the atomic nucleus.

• Beauty - Bohr
  Bohr Model: Suggested that electrons move in fixed orbits around the nucleus, and energy is absorbed or emitted when electrons jump between these orbits.
  Example: Bohr’s model of the hydrogen atom explained the discrete lines in its emission spectrum.

Thomson Model Features

Types: Plum Pudding, Positive Sphere, Embedded Electrons

Mnemonic: "Priya Pours Electric Power"

Breakdown:

• Priya - Plum Pudding
  Plum Pudding Model: Thomson proposed that the atom is like a "plum pudding," where negatively charged electrons are embedded in a positively charged "soup" or sphere.
  Example: In this model, the positive charge is spread throughout the atom, with electrons scattered inside.

• Pours - Positive Sphere
  Positive Sphere: In the Plum Pudding model, the atom’s positive charge is spread uniformly over the entire atom, like the pudding around the "plums" (electrons).
  Example: The positive charge in the atom ensures the overall neutrality when combined with the negatively charged electrons.

• Electric Power - Embedded Electrons
  Embedded Electrons: Electrons are embedded in the positive charge of the atom, much like plums in a pudding, and they move freely within this positively charged sphere.
  Example: The electrons in Thomson’s model are held in place by the positive charge of the sphere, but can move freely inside.

Rutherford Experiment Observations

Types: Scattering, Nucleus, Empty Space

Mnemonic: "Some Nuclei Emit Signals"

Breakdown:

• Some - Scattering
  Scattering: Rutherford observed that most alpha particles passed through the gold foil with little or no deflection, but some were scattered at large angles, indicating that atoms have a dense core.
  Example: The scattering of alpha particles helped demonstrate that the atom is not solid, but has a central nucleus.

• Nuclei - Nucleus
  Nucleus: The experiment revealed that the atom has a tiny, dense, positively charged nucleus at its center, where most of the atom’s mass is concentrated.
  Example: The nucleus holds protons and neutrons and is responsible for the atom’s overall mass.

• Emit Signals - Empty Space
  Empty Space: Rutherford’s experiment showed that the majority of an atom is empty space, as most alpha particles passed through the gold foil without significant deflection.
  Example: This empty space is the region between the dense nucleus and the orbiting electrons.

Bohr Model Postulates

Types: Quantized Orbits, Energy Levels, Electron Transitions

Mnemonic: "Quickly Elevating Every Thought "

Breakdown:

• Quickly - Quantized Orbits
  Quantized Orbits: Electrons revolve in specific, fixed orbits with quantized energies. They cannot exist between these orbits.
  Example: Electrons move in these distinct orbits around the nucleus without radiating energy unless they transition to a different orbit.

• Elevating - Energy Levels
  Energy Levels: The electron orbits correspond to different energy levels. The energy is lower closer to the nucleus and higher further away.
  Example: Energy levels are discrete, meaning electrons can only have certain energy values depending on their orbit.

• Every Thought - Electron Transitions
  Electron Transitions: When an electron moves between energy levels, it either absorbs or emits energy in the form of light. The energy change corresponds to the difference between the two energy levels.
  Example: When an electron jumps to a higher energy level, it absorbs energy, and when it returns to a lower level, it emits light (specific wavelengths).