Atomic Structure and Chemical Bonding

Atoms are the fundamental building blocks of matter.
Atoms consist of a nucleus containing protons and neutrons, surrounded by orbiting electrons.
Protons have a positive charge, neutrons are neutral, and electrons have a negative charge.
The number of protons in an atom defines its atomic number, which uniquely identifies an element.
Different isotopes of an element have the same number of protons but a different number of neutrons, resulting in variations in atomic mass.
Electrons orbit the nucleus in specific energy levels or shells.
The arrangement of electrons in the different energy levels determines the chemical properties of an element.
The outermost shell of electrons is called the valence shell, and its electrons are involved in chemical bonding.

Chemical bonds hold atoms together to form molecules.
The three main types of chemical bonds are ionic, covalent, and metallic bonds.
Ionic bonds form when one or more electrons are transferred from one atom to another, creating positively and negatively charged ions which attract each other.
Covalent bonds form when atoms share one or more pairs of electrons.
Metallic bonds occur in metals where the valence electrons are delocalized, creating a strong attraction between the positively charged metal ions and the surrounding sea of electrons.
The strength and type of bonds influence the physical properties of substances.

Chemical reactions involve the rearrangement of atoms to form new substances.
Reactants are the substances that undergo change, and products are the substances formed.
Chemical equations represent chemical reactions, showing the reactants and products, and their relative amounts.
Chemical reactions are either exothermic (releasing heat) or endothermic (absorbing heat).
Balancing chemical equations ensures conservation of mass.
The rate of a chemical reaction depends on factors like temperature, concentration, and catalysts.
Acids and bases are special types of compounds that react in characteristic ways, often with the production of salts and water.

Matter exists in three primary states: solid, liquid, and gas.
Solids have a fixed shape and volume, liquids have a fixed volume but take the shape of their container, gases have neither a fixed shape nor volume.
These states differ significantly in molecular arrangement and movement.
Phase transitions occur as matter changes from one state to another, requiring an input or release of energy.
Examples of phase transitions include melting, freezing, vaporization, condensation, and sublimation.

Solutions are homogeneous mixtures of two or more substances.
The solute is the substance being dissolved, and the solvent is the substance doing the dissolving.
Concentration describes the amount of solute in a given amount of solution.
Concentration can be expressed in various ways, such as molarity, molality, and percent by mass.
Solubility describes the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.

The periodic table organizes elements based on their atomic number and recurring chemical properties.
Elements are arranged in rows called periods and columns called groups.
Elements in the same group exhibit similar chemical properties due to their similar valence electron configurations.
The periodic table provides a visual representation of trends in atomic properties such as atomic radius, ionization energy, and electronegativity.
Understanding the periodic table is crucial for predicting the behavior and properties of elements.

Acids are substances that release hydrogen ions (H+) in aqueous solution.
Bases are substances that release hydroxide ions (OH−) in aqueous solution or accept H+.
The pH scale measures the acidity or basicity of a solution.
Acids have a pH less than 7, bases have a pH greater than 7, and neutral solutions have a pH of 7.
Strong acids and bases completely ionize in solution, while weak acids and bases only partially ionize.

Chemical kinetics studies the rates of chemical reactions.
Factors affecting reaction rates, including temperature, concentration, and catalysts, are key considerations.
Equilibrium is a state in which the rates of the forward and reverse reactions are equal.
The law of mass action describes the relationship between the concentrations of reactants and products at equilibrium.
Le Chatelier's principle describes how a change in conditions (temperature, pressure, concentration) affects the position of equilibrium.

Thermodynamics deals with energy changes during chemical and physical processes.
Entropy (S) measures disorder or randomness in a system.
Enthalpy (H) quantifies the heat content of a system.
Gibbs free energy (G) determines whether a process is spontaneous.
The relationship between enthalpy, entropy, and temperature determines the spontaneity of a process.