Chemistry: Atomic Structure and Bonding

Atomic Structure

• Atoms are the fundamental building blocks of matter.
• Atoms consist of a nucleus containing protons (positively charged) and neutrons (neutral).
• Electrons (negatively charged) orbit the nucleus.
• The number of protons determines the element.
• Atomic number = number of protons.
• Atomic mass = number of protons + number of neutrons.
• Isotopes are atoms of the same element with different numbers of neutrons.
• Electron configuration describes the arrangement of electrons in energy levels and orbitals around the nucleus.

Chemical Bonding

• Chemical bonds are forces that hold atoms together in molecules and compounds.
• Ionic bonds form between metals and nonmetals, involves the transfer of electrons.
• Covalent bonds form between nonmetals, involve the sharing of electrons.
• Metallic bonds occur between metal atoms, characterized by a "sea" of delocalized electrons.
• Hydrogen bonds are a special type of dipole-dipole interaction between a hydrogen atom bonded to a highly electronegative atom (like oxygen or nitrogen) and another electronegative atom.
• Van der Waals forces are weak attractive forces between molecules, including London Dispersion Forces.

Periodic Table

• The periodic table arranges elements by atomic number and recurring chemical properties.
• Elements are grouped into periods (rows) and groups (columns).
• Elements in the same group have similar chemical properties due to similar valence electron configurations.
• Metals are generally good conductors of heat and electricity, while nonmetals are poor conductors.
• Metalloids have properties intermediate between metals and nonmetals.
• Trends in the periodic table include atomic radius, ionization energy, electronegativity, and metallic character.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactants are the starting substances, and products are the resulting substances.
• Chemical equations represent chemical reactions, showing the reactants and products, including their states of matter (solid, liquid, gas, aqueous).
• Balancing chemical equations ensures that the number of atoms of each element is the same on both sides of the equation.
• Types of chemical reactions include synthesis, decomposition, single displacement, double displacement, combustion, and acid-base reactions.
• Different reaction types have different characteristics and predictable products based on the reactants.

States of Matter

• Matter exists in different states, including solid, liquid, and gas.
• Solids have a definite shape and volume.
• Liquids have a definite volume but take the shape of their container.
• Gases have neither a definite shape nor a definite volume.
• Phase transitions describe changes between states (e.g., melting, freezing, vaporization, condensation, sublimation).
• Changes in temperature and pressure affect the state of matter.

Stoichiometry

• Stoichiometry deals with quantitative relationships in chemical reactions.
• Stoichiometric calculations relate amounts of reactants and products using balanced chemical equations.
• Moles are a unit for measuring the amount of substance.
• Molar mass is the mass of one mole of a substance, which provides a way to convert between mass and moles.
• Calculations can include determining limiting reactants, predicting product yields, and calculating empirical formulas.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• A solute is the substance dissolved, and a solvent is the substance doing the dissolving.
• Concentration describes the amount of solute present in a given amount of solvent or solution.
• Factors affecting solubility include temperature, pressure, and the nature of the solute and solvent.
• Solutions can be categorized based on their concentration using different units like molarity, molality, or percentage by mass.

Acids and Bases

• Acids and bases are chemical substances that exhibit specific properties in aqueous solutions.
• Acids are proton donors (releasing H+ ions), while bases are proton acceptors (accepting H+ ions).
• The pH scale measures the acidity or basicity of a solution.
• Neutralization reactions occur when acids and bases react to form water and a salt.

Redox Reactions

• Redox reactions involve the transfer of electrons between reactants.
• Oxidation is the loss of electrons, and reduction is the gain of electrons.
• Redox reactions are common in many chemical processes.

Thermodynamics

• Thermodynamics deals with energy changes in chemical and physical processes.
• First Law of Thermodynamics (Conservation of energy): energy cannot be created or destroyed, only transferred or transformed.
• Second Law of Thermodynamics: the total entropy of an isolated system can only increase over time.

Kinetics

• Chemical kinetics studies the rates of chemical reactions.
• Factors that affect reaction rates include temperature, concentration, surface area, catalysts, and the presence of inhibitors.
• Reaction mechanisms describe the step-by-step process of a reaction.