Qualitative Chemistry: Rutherford's Model Limitations

The model is analogous to a solar system, where planets are neutral and influenced by gravitational forces, unlike negatively charged electrons that repel each other.
According to Maxwell's theory, moving charge results in continuous energy emission, causing electrons to spiral into the nucleus, making the model implausible.
The predicted atom spectrum should present continuous lines but observed spectra show distinct and bright lines.
There is no explanation for the shape and size of electron orbits around the nucleus in this model.
The model fails to account for the electron movement in atoms with multiple electrons.

Niels Bohr introduced his atomic model in 1913 to address the limitations of Rutherford's model.
Bohr's model is built on Max Planck's quantum theory of radiation, proposing that matter absorbs or emits energy in discrete packets known as "quanta."
This model incorporates quantized orbits for electrons, leading to stable electron arrangements and explaining the atomic emission spectrum more accurately.

Qualitative chemistry focuses on identifying chemical constituents in substances instead of measuring quantities.

Element Identification: Involves techniques for identifying present elements in a sample.
Compound Composition: Analyzes the types and functional groups of compounds in a sample.

Flame Tests:
- Identify metal ions through the colors emitted when heated.
- Example: Sodium ions produce a bright yellow flame.
Precipitation Reactions:
- Mixing solutions creates an insoluble solid (precipitate), signaling specific ions' presence.
- Example: Barium chloride mixed with sodium sulfate produces barium sulfate precipitate.
pH Testing:
- Assesses a solution's acidity or basicity, indicating the presence of acids or bases.
- Quick results can be obtained using pH indicators like litmus paper.
Chromatography:
- Separates mixture components based on their movement through a stationary phase.
- Valuable for identifying pigments, dyes, or other substances.
Spectroscopy:
- Techniques like UV-Vis and IR spectroscopy identify substances by their interaction with electromagnetic radiation.
- Useful for determining functional groups and molecular structures.

Environmental Analysis: Identifies pollutants in air, water, and soil.
Forensic Chemistry: Analyzes crime scene substances to identify drugs, toxins, and materials.
Pharmaceuticals: Verifies active ingredients and contaminant absence in drugs.

Qualitative methods do not measure substance amounts.
Results require careful interpretation, as techniques might produce unclear or overlapping signals.

Essential for providing foundational information leading to quantitative analysis.
Enhances understanding of chemical behavior and interactions in fields like biochemistry and materials science.