Chemistry: Atomic Structure and Chemical Bonds

Atomic Structure

• Atoms are the fundamental building blocks of matter.
• Atoms consist of a nucleus containing protons and neutrons, with electrons orbiting the nucleus.
• Protons carry a positive charge, neutrons are neutral, and electrons carry a negative charge.
• The number of protons in an atom defines its atomic number and determines the element.
• Atoms strive for stability, often achieving this through the formation of chemical bonds.

Elements and Compounds

• Elements are pure substances composed of only one type of atom.
• Compounds are pure substances composed of two or more different elements chemically bonded together.
• Elements are organized on the periodic table based on their atomic number and properties.
• The periodic table displays trends in atomic properties, such as ionization energy and electronegativity.
• Compounds have unique properties distinct from those of their constituent elements.

Chemical Bonding

• Chemical bonds are attractive forces that hold atoms together.
• Ionic bonds form between a metal and a nonmetal, involving the transfer of electrons.
• Covalent bonds form between nonmetals, involving the sharing of electrons.
• Metallic bonds occur between metals, characterized by a sea of delocalized electrons.
• Hydrogen bonds are a special type of dipole-dipole interaction, critical for the properties of water and biological molecules.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactions are represented by chemical equations, showing reactants and products.
• Chemical reactions can be classified based on different factors, such as oxidation-reduction (redox) reactions, acid-base reactions, and precipitation reactions.
• Stoichiometry is the quantitative study of reactants and products in chemical reactions.

States of Matter

• Matter exists in three primary states: solid, liquid, and gas, each with unique properties.
• Solids have fixed shape and volume, liquids have a fixed volume but variable shape, and gases have neither fixed shape nor volume.
• Changes in temperature and pressure can affect the state of matter.
• Phase transitions involve changes between these states, such as melting, freezing, vaporization, condensation, and sublimation.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• The solvent is the substance present in the greater amount, and the solute is the substance dissolved in the solvent.
• Solutions can be described by their concentration, which quantifies the amount of solute dissolved in a given amount of solvent.
• Solubility is the ability of a substance to dissolve in a given solvent.

Acids and Bases

• Acids are substances that release hydrogen ions (H+) when dissolved in water.
• Bases are substances that release hydroxide ions (OH-) when dissolved in water.
• The pH scale measures the acidity or basicity of a solution.
• Neutralization reactions occur when an acid and a base react, producing a salt and water.

Thermodynamics

• Thermodynamics is the study of energy transfer in chemical and physical processes.
• Key concepts include enthalpy (heat content), entropy (disorder), and Gibbs free energy (energy available for work).
• Exothermic reactions release heat, while endothermic reactions absorb heat.
• Chemical reactions occur spontaneously if the Gibbs free energy change is negative.

Kinetics

• Chemical kinetics studies the rates of chemical reactions.
• Factors affecting reaction rates include temperature, concentration of reactants, catalysts, and surface area.
• Reaction rates are dependent on the activation energy, the minimum energy required for a reaction to occur.
• Reaction mechanisms describe the individual steps involved in a chemical reaction.

Organic Chemistry

• Organic chemistry focuses on the study of carbon-containing compounds.
• Organic molecules exhibit diverse structures, from simple hydrocarbons to complex biomolecules.
• Functional groups define the specific properties of organic molecules.
• Organic chemistry plays a crucial role in understanding biological, industrial, and material processes.