Atomic Structure and Chemical Bonding

Atomic Structure

• Atoms are the fundamental building blocks of matter, composed of a nucleus containing protons and neutrons, surrounded by electrons in orbitals.
• Protons have a positive charge, neutrons are neutral, and electrons have a negative charge.
• The number of protons defines the element, and the atomic number.
• Isotopes are atoms of the same element with a different number of neutrons.
• Atomic mass is the average mass of all naturally occurring isotopes of an element.

Chemical Bonding

• Atoms bond together to form molecules and compounds through the sharing or transferring of electrons.
• Ionic bonds form when electrons are transferred from one atom to another, creating ions with opposite charges that attract.
• Covalent bonds form when atoms share electrons.
• Metallic bonds occur in metals, where valence electrons are delocalized and shared among a lattice of positive ions.
• Intermolecular forces are attractive forces between molecules, weaker than bonds between atoms.

Periodic Table

• The periodic table organizes elements by atomic number and recurring chemical properties.
• Elements are arranged in periods (rows) and groups (columns).
• Elements in the same group have similar chemical properties because they have the same number of valence electrons.
• Metals are generally good conductors of heat and electricity, and are located on the left side of the table.
• Nonmetals are generally poor conductors of heat and electricity, and are located on the right side of the table.
• Metalloids exhibit properties of both metals and nonmetals.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactants are the starting materials, and products are the resulting substances.
• Chemical equations represent chemical reactions, showing the reactants and products and their relative amounts.
• Balanced chemical equations show equal numbers of each type of atom on both sides of the equation.
• Types of chemical reactions include synthesis, decomposition, single displacement, double displacement (metathesis), and 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.
• Gases have neither a definite shape nor a definite volume.
• Phase changes (e.g., melting, freezing, vaporization, condensation, sublimation) involve changes in the state of matter.

Stoichiometry

• Stoichiometry is the calculation of the quantities of reactants and products in a chemical reaction.
• Mole concept is crucial for stoichiometric calculations, relating the number of particles to their mass.
• Molar mass is the mass of one mole of a substance.
• Limiting reactants are the reactants that control the amount of product formed.

Acids and Bases

• Acids are substances that produce hydrogen ions (H+) when dissolved in water.
• Bases are substances that produce hydroxide ions (OH-) when dissolved in water.
• pH is a measure of the acidity or basicity of a solution.
• The pH scale ranges from 0 to 14, with 7 being neutral.
• Strong acids and bases completely ionize in water, while weak acids and bases only partially ionize.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• A solute is the substance dissolved in a solvent.
• Concentration is the amount of solute in a given amount of solvent or solution.
• Solubility is the ability of a substance to dissolve in a solvent.
• Factors affecting solubility include temperature, pressure, and nature of solute and solvent.

Thermodynamics

• Thermodynamics deals with energy changes in chemical and physical processes.
• First law of thermodynamics: Energy cannot be created or destroyed, only transferred or changed from one form to another.
• Second law of thermodynamics: The total entropy of an isolated system can only increase over time.
• Third law of thermodynamics: The entropy of a perfect crystal at absolute zero is zero.

Kinetics

• Kinetics studies the rates of chemical reactions.
• Reaction rate is the speed at which reactants are converted to products.
• Factors influencing reaction rates include temperature, concentration, surface area, and catalysts.
• Activation energy is the minimum energy required for a reaction to occur.