Lecture Notes: Introduction to Atoms, Chemistry, and Molecular Structure

Atoms and Basic Chemistry

• Atoms: Basic building blocks of matter, consisting of a core (protons and neutrons) and electrons.
• Elements: Types of atoms characterized by the number of protons.
• Periodic Table: Lists all elements; organized by valence electrons (groups) and electron shells (periods).
• Valence Electrons: Electrons in the outermost shell, crucial in chemical reactions.

Molecular Structure and Bonds

• Molecules and Compounds: Two or more atoms bonded; compounds contain different elements.
• Chemical Bonds:
  • Covalent Bonds: Sharing of electrons.
  • Ionic Bonds: Transfer of electrons between atoms with large electronegativity differences.
  • Metallic Bonds: "Delocalized" electrons in a grid of metal nuclei.
  • Van der Waals Forces: Weak attraction due to temporary dipoles.
  • Hydrogen Bonds: Strong dipoles between hydrogen and electronegative atoms (e.g., O, N, F).

Chemical Reactions and Stoichiometry

• Types of Reactions: Synthesis, Decomposition, Single and Double Replacement.
• Stoichiometry: Ratio of reactants and products in reactions, based on conservation of mass.
• Moles: Measurement unit for amount of substance based on atomic mass.

Thermodynamics and Reaction Energy

• Energy Changes:
  • Exothermic Reactions: Release energy (e.g., burning wood).
  • Endothermic Reactions: Absorb energy.
  • Activation Energy: Energy needed to start a reaction.
• Gibbs Free Energy: Determines spontaneity considering enthalpy, entropy, and temperature.

Acids, Bases, and pH

• Acids and Bases (Bronsted-Lowry):
  • Acid: Proton donor.
  • Base: Proton acceptor.
• pH Scale: Measures acidity; lower values indicate higher acidity.

Advanced Topics in Chemistry

• Quantum Mechanics:
  • Quantum Numbers: Describe electrons (n, l, ml, ms).
  • Electron Configuration: Order of filling electron subshells (Aufbau principle).
• Oxidation-Reduction (Redox) Reactions: Involve changes in oxidation states due to electron transfer.

States of Matter

• Solid, Liquid, Gas: Defined by particle arrangement and movement.
• Plasma: Ionized gas at high temperature or potential.

Mixtures and Solutions

• Types of Mixtures:
  • Homogeneous: Even distribution (e.g., salt in water).
  • Heterogeneous: Uneven distribution (e.g., sand in water).
  • Colloids: Intermediate particle size (e.g., milk).

Conclusion

• Chemistry revolves around atomic structure, electron configuration, and the interactions and bonds between atoms and molecules.
• Practical applications include understanding material properties, chemical reactivity, and energy changes in reactions.