Atomic Structure and Chemical Bonding

Atomic Structure

• Atoms are the fundamental building blocks of matter, composed of protons, neutrons, and electrons.
• Protons have a positive charge, electrons have a negative charge, and neutrons are neutral.
• The nucleus of an atom contains protons and neutrons, while electrons orbit the nucleus in electron shells.
• Atomic number is the number of protons in an atom, defining the element.
• Atomic mass is the sum of protons and neutrons.
• Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses.

Chemical Bonding

• Chemical bonds hold atoms together to form molecules and compounds.
• Ionic bonds form between a metal and a nonmetal, involving electron transfer.
• Covalent bonds form between two nonmetals, involving electron sharing.
• Metallic bonds occur between metal atoms, exhibiting a "sea" of delocalized electrons.
• Hydrogen bonds are a special dipole-dipole interaction, influencing water and biological molecules' properties.
• Van der Waals forces are weak attractions between molecules due to temporary electron fluctuations.

States of Matter

• Matter exists in three primary states: solid, liquid, and gas.
• Solids have a definite shape and volume, with tightly packed particles.
• Liquids have a definite volume but take the container's shape, with less tightly packed particles.
• Gases have neither definite shape nor volume, with widely spaced, constantly moving particles.
• Plasma is a state of matter consisting of ionized gas.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactants undergo change, while products are formed.
• Chemical equations represent reactions, showing reactants on the left and products on the right.
• Types of chemical reactions include synthesis, decomposition, single displacement, double displacement, and combustion.
• Reactions can be exothermic (releasing heat) or endothermic (absorbing heat).
• Stoichiometry deals with the quantitative relationships between reactants and products in a chemical reaction.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• A solution consists of a solute dissolved in a solvent.
• Concentration measures the amount of solute in a given amount of solvent or solution.
• Solubility is the maximum solute amount dissolving in a given solvent at a specific temperature and pressure.
• Factors affecting solubility include temperature, pressure, and solute/solvent nature.

Acids and Bases

• Acids donate protons (H+) in solution.
• Bases accept protons or donate hydroxide ions (OH-).
• The pH scale measures solution acidity/basicity, ranging from 0 to 14.
• Neutralization reactions occur when an acid and a base react, forming water and a salt.

Thermodynamics

• Thermodynamics deals with energy changes in chemical and physical processes.
• The first law of thermodynamics states energy cannot be created or destroyed, only transformed.
• The second law of thermodynamics states the total entropy of an isolated system always increases over time.
• The third law of thermodynamics states the entropy of a perfect crystal at absolute zero is zero.

Kinetics

• Chemical kinetics studies reaction rates.
• Reaction rates depend on temperature, reactant concentration, and catalysts.
• Collision theory explains reactant molecule collisions needing sufficient energy and proper orientation to react.
• Catalysts speed up reactions by lowering the activation energy.