Chemistry Overview: Branches and Structure

Branches of Chemistry

• Chemistry is the study of matter, its properties, how it changes, and the energy involved in these changes.
• Branches of chemistry include organic chemistry (carbon-containing compounds), inorganic chemistry (non-carbon compounds), physical chemistry (deals with properties and behavior of matter), analytical chemistry (identifying and quantifying substances), and biochemistry (chemical processes in living organisms).

Atomic Structure

• Atoms are the basic building blocks of matter, consisting of a nucleus (containing protons and neutrons) surrounded by electrons.
• Protons have a positive charge, electrons have a negative charge, and neutrons are neutral.
• The atomic number is the number of protons in an atom, determining the element.
• The mass number is the sum of protons and neutrons in an atom.
• Isotopes are atoms of the same element with different numbers of neutrons but the same amount of protons.

Chemical Bonding

• Chemical bonds hold atoms together in molecules and compounds.
• Types of chemical bonds include:
  • Ionic bonds: Formed by the transfer of electrons between atoms, creating ions (charged particles) that attract each other.
  • Covalent bonds: Formed by the sharing of electrons between atoms. Covalent bonds can be polar (unequal sharing) or nonpolar (equal sharing).
  • Metallic bonds: Formed by the attraction between metal ions and a "sea" of delocalized electrons.

Chemical Reactions

• Chemical reactions are processes in which one or more substances are transformed into new substances.
• Key characteristics include:
  • Reactants are substances undergoing transformation.
  • Products are resulting substances.
  • A chemical equation describes the reaction, showing reactants and products.
• Types of chemical reactions include:
  • Combination reactions (synthesis).
  • Decomposition reactions.
  • Single replacement reactions.
  • Double replacement reactions.
  • Combustion reactions (reaction with oxygen to produce heat and light).

Stoichiometry

• Stoichiometry is the quantitative study of reactants and products in chemical reactions.
• Concepts include:
  • Mole concept: A mole is a unit of measurement for the amount of a substance.
  • Molar mass: The mass of one mole of a substance.
  • Balancing chemical equations: Ensure the same number of each element are on both sides of the equation
  • Limiting reactants: The reactant that is completely consumed in the reaction, limiting how much product can be formed.
  • Percent yield: The ratio of actual yield to theoretical yield.

Solutions

• Solutions are homogeneous mixtures of two or more substances, consisting of a solute (dissolved substance) and a solvent (dissolving substance).
• Concentration is a measure of the amount of solute present in a solution.
• Units include molarity, molality, and percentage.
• Colligative properties depend on the concentration of solute particles but not on their identity, such as boiling point elevation and freezing point depression.

Acids and Bases

• Acids and bases are chemical substances that affect the acidity or basicity of a solution.
• Acids typically contain hydrogen ions (H+) and bases typically contain hydroxide ions (OH-).
• The pH scale measures the concentration of hydrogen ions in a solution.
• Strong acids and bases completely dissociate in water, while weak acids and bases only partially dissociate.
• Neutralization reactions occur when acids and bases react to form water and a salt.

Thermodynamics

• Thermodynamics deals with energy changes in chemical reactions.
• Concepts include:
  • Enthalpy (ΔH): Heat absorbed or released during a reaction.
  • Entropy (ΔS): Measure of disorder or randomness in a system.
  • Gibbs free energy (ΔG): The overall energy available to do work in a system.
• Exothermic reactions release heat (ΔH < 0), and endothermic reactions absorb heat (ΔH > 0).

Kinetics

• Chemical kinetics studies the rates of chemical reactions.
• Factors affecting reaction rates include concentration of reactants, temperature, catalysts, and surface area of reactants.
• Reaction mechanisms are the step-by-step processes of chemical reactions.

Organic Chemistry

• This branch focuses on carbon-containing compounds, which form the basis of many biological molecules.
• Types of organic compounds include:
  • Alkanes (single bonds), alkenes (double bonds), alkynes (triple bonds).
  • Functional groups determine the properties of organic molecules.

Nuclear Chemistry

• This branch studies the structure and properties of atomic nuclei and radioactive processes.
• Radioactive decay, nuclear fission, and nuclear fusion are important applications in nuclear chemistry.