Chemistry Basics: Atoms, Elements, and Compounds

Atoms

• Composition: Atoms consist of a core (protons and neutrons) and electrons.
• Elements: Defined by the number of protons in the core.
• Electron Shells: Electrons occupy multiple shells, outermost called "valence electrons".
• Periodic Table: Elements with similar valence electrons show similar chemical behavior.
• Ions: Atoms with unequal numbers of protons and electrons, charged either positively (cations) or negatively (anions).
• Isotopes: Variants with different numbers of neutrons.

Periodic Table

• Groups: Elements in the same group have the same number of valence electrons.
• Periods: Elements in the same period have the same number of electron shells.
• Categories:
  • Metals
  • Non-metals
  • Semimetals

Molecules and Compounds

• Molecules: Two or more atoms bonded together.
• Compounds: Molecules with at least two different elements.
• Writing Molecules:
  • Molecular formula
  • Lewis-Dot-Structure (represents valence electrons and bonds)
• Chemical Bonds:
  • Covalent Bonds (sharing electrons)
  • Ionic Bonds (transfer of electrons)
  • Metallic Bonds (delocalized electrons)

Bonding and Periodic Trends

• Valence Shell: Full valence shells achieve lower energy, stability.
• Electronegativity: Measure of an atom’s ability to attract shared electrons.
• Bond Types:
  • Covalent (sharing)
  • Ionic (transferring)
  • Metallic (free-moving electrons)

Forces and Interactions

• Intermolecular Forces (IMFs): Forces between molecules
  • Hydrogen bonds
  • Van der Waals forces
• Solubility:
  • "Like dissolves like"
  • Polarity influences solubility

States of Matter

• Solid: Fixed structure, particles vibrate.
• Liquid: Particles move freely but confined to volume.
• Gas: Particles fill available volume.
• Temperature & Entropy: Affect state of matter.

Reactions and Energy

• Chemical Reactions:
  • Synthesis
  • Decomposition
  • Single Replacement
  • Double Replacement
• Stoichiometry: Ratio of reactants based on conservation of mass.
• Energy:
  • Enthalpy (heat content)
  • Gibbs Free Energy (determines spontaneity)
• Catalysts: Reduce activation energy without being consumed.

Acids, Bases, and pH

• Acids/Bases (Bronsted-Lowry): Proton donors/acceptors.
• pH Scale: Measures acidity, based on hydronium ion concentration.
• Neutralization: Acid-base reaction forming water and salt.

Quantum Mechanics & Electron Configuration

• Quantum Numbers: Describe electron arrangements.
• Electron Configuration: Order of filling subshells based on energy levels.
• Aufbau Principle: Order of electron fill-in subshells.

Conclusion

• Chemistry principles cover atomic structure, periodic trends, bonding, interactions, states of matter, chemical reactions, energy, acids/bases, and electron configurations.