Essential Chemistry Concepts: Separation, Bonding, and Models

Heterogeneous Mixture Separation

• Filtration: Separates a solid from a liquid using filter paper that allows the liquid to pass while retaining the solid.
• Decantation: Separates two immiscible liquids with different densities.
• Magnetic Separation: Uses a magnet to extract ferromagnetic components from a mixture.
• Centrifugation: Separates suspensions of solids and liquids by spinning the mixture to force solids outward.

Homogeneous Mixture Separation

• Chromatography: Separates liquids with different densities and colors using paper, where the lower density liquid rises.
• Extraction by Solvents: Separates two liquids based on their different solubilities in a specific solvent.
• Distillation: Separates two liquids with different boiling points by heating the mixture to boil off the liquid with the lower boiling point.
• Crystallization: Separates a solid solute from a liquid solvent by evaporating the liquid to form solid crystals.

The Periodic Table

The periodic table was developed by Mendeleev in 1870. Elements are arranged in increasing order of atomic number.

• Structure: 18 groups (columns) and 7 periods (rows).
• Blocks: Left (S2: alkali and alkaline earth metals), Middle (D10: transition elements), Right (P6: halogens and noble gases), Bottom (F14: lanthanides and actinides).
• Classification: Metals are located below the stair-step line, while non-metals are to the right. Semi-metals include silicon and germanium.

Chemical Bonding

• Ionic Bonding: Occurs between metals and non-metals. Metals donate electrons to become cations, while non-metals accept them to become anions.
• Covalent Bonding: Involves sharing electron pairs between non-metals that tend to accept electrons.
• Metallic Bonding: Explained by the electron cloud theory:
  • A tridimensional net of nuclei with complete inner electron levels.
  • A cloud of free-moving electrons shared by all atoms in the net.

Atomic Models

• Bohr Model: Electrons occupy specific allowed orbits; they jump to outer orbits by absorbing energy and inner orbits by emitting energy.
• Thomson Model: Atoms consist of positively charged, jelly-like matter with electrons embedded throughout to maximize separation.
• Rutherford Model: Atoms are mostly hollow, featuring a small, dense, positively charged nucleus with electrons spinning far away.

Kinetic Theory

The study of the microscopic behavior of molecules and the interactions that lead to macroscopic relationships.