Atomic Structure and Chemical Bonding

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, electrons carry a negative charge, and neutrons have no charge.
• The number of protons in an atom's nucleus defines its atomic number, which determines the element.
• Atoms are mostly empty space. The volume occupied by the nucleus is negligible compared to the overall atomic volume.
• Electrons occupy specific energy levels or shells around the nucleus. Each shell can hold a maximum number of electrons.
• Atoms can gain or lose electrons to form ions.
• Isotopes are atoms of the same element that have different numbers of neutrons. They have the same atomic number but different mass numbers.

Chemical Bonding

• Atoms bond to each other to achieve a more stable electron configuration, often a full outer electron shell.
• Ionic bonds form when one atom gives up electrons to another atom, creating ions with opposite charges that attract each other.
• Covalent bonds form when atoms share electrons to achieve a full outer shell.
• Metallic bonds result from the attraction between metal cations and a "sea" of delocalized electrons.
• Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond.

Chemical Reactions

• Chemical reactions involve the breaking and forming of chemical bonds.
• Reactants are the substances that undergo a chemical change, and products are the substances produced.
• Chemical equations represent chemical reactions. They show the reactants and products and the relative amounts of each substance.
• The Law of Conservation of Mass dictates that the total mass of reactants must equal the total mass of products in a chemical reaction.
• Chemical reactions can be classified based on different factors (e.g., synthesis, decomposition, single replacement, double replacement, combustion).

States of Matter

• Matter exists in three primary states: solid, liquid, and gas.
• Solids have a definite shape and volume, liquids have a definite volume but take the shape of their container, and gases have neither a definite shape nor volume.
• Changes of state involve the absorption or release of energy.
• Phase diagrams show the conditions (temperature and pressure) under which different states of a substance exist.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• The solute dissolves in the solvent.
• The concentration of a solution describes the amount of solute present in a given amount of solvent or solution. Units include molarity, molality, and percent by mass.
• Solubility refers to the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure.
• Factors affecting solubility include temperature, pressure (often for gases), and the nature of the solute and solvent.

Thermodynamics

• Thermodynamics deals with energy changes in chemical and physical processes.
• The first law of thermodynamics, the Law of Conservation of Energy, states that energy cannot be created or destroyed, only transformed.
• The second law of thermodynamics describes the tendency of systems to move toward disorder or entropy.
• The third law of thermodynamics describes the behavior of systems as the temperature approaches absolute zero.
• Enthalpy (H) is a measure of the system's heat content, and a change in enthalpy (ΔH) can be used to determine whether a reaction is exothermic (release heat) or endothermic (absorb heat).

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. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic.
• Strong acids and bases ionize completely in water, while weak acids and bases only partially ionize.
• Neutralization reactions occur when acids and bases react to form a salt and water.

Kinetics

• Chemical kinetics studies the rates of chemical reactions.
• Factors affecting reaction rates include the concentration of reactants, temperature, presence of a catalyst, and surface area.
• Reaction mechanisms are the stepwise series of elementary reactions by which the overall reaction occurs.
• Activation energy is the minimum energy required for a reaction to proceed.

Redox Reactions

• Redox reactions involve the transfer of electrons between species.
• Oxidation is the loss of electrons, and reduction is the gain of electrons.
• Oxidizing agents cause oxidation, and reducing agents cause reduction.
• Balancing redox reactions typically involves identifying which atoms undergo changes in oxidation states.

Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds.
• Carbon has a unique ability to form chains and rings, leading to a huge variety of organic molecules.
• Functional groups are specific groups of atoms within organic molecules that determine many of the molecule's properties, such as reactivity.

Nuclear Chemistry

• Nuclear chemistry studies the structure and properties of atomic nuclei.
• Radioactive isotopes undergo radioactive decay, releasing particles or energy in the process.
• Nuclear reactions can be used in various applications including medical imaging, power generation, and industrial processes including dating.