Basic Concepts of Chemistry

Matter: Anything that has mass and occupies space; exists in solid, liquid, or gas states.
Atoms: Basic units of matter; consist of protons, neutrons, and electrons.
Elements: Pure substances made of only one type of atom; represented on the periodic table.

Nucleus: Center of an atom; contains protons (positive charge) and neutrons (neutral charge).
Electrons: Negatively charged particles that orbit the nucleus in electron shells.
Atomic Number: Number of protons in an atom; defines the element.
Mass Number: Total number of protons and neutrons in an atom.

Ionic Bonds: Formed through the transfer of electrons from one atom to another; results in charged ions.
Covalent Bonds: Formed by the sharing of electrons between atoms.
Metallic Bonds: Occur between metal atoms; electrons are shared in a "sea of electrons."

Reactants: Substances that undergo a change in a chemical reaction.
Products: Substances formed as a result of a chemical reaction.
Types of Reactions:
- Synthesis: Two or more substances combine to form a new compound.
- Decomposition: A single compound breaks down into two or more simpler substances.
- Single Replacement: An element replaces another in a compound.
- Double Replacement: Exchange of ions between two compounds.

Solid: Definite shape and volume; particles packed closely together.
Liquid: Definite volume but takes the shape of its container; particles are loosely packed.
Gas: No definite shape or volume; particles are far apart and move freely.

Acids: Substances that donate protons (H+) in a solution; pH < 7.
Bases: Substances that accept protons or donate hydroxide ions (OH-); pH > 7.
pH Scale: Measures acidity or basicity; ranges from 0 (acidic) to 14 (basic).

Groups: Vertical columns; elements in the same group have similar properties.
Periods: Horizontal rows; indicate energy levels of electrons.
Metals, Nonmetals, Metalloids: Classification based on properties; metals are conductive and malleable, nonmetals are poor conductors, metalloids have mixed properties.

Mole: The amount of substance containing as many entities as there are atoms in 12 grams of carbon-12.
Molar Mass: The mass of one mole of a substance, calculated by summing the atomic masses of its elements.
Balanced Equations: Chemical equations must be balanced to obey the law of conservation of mass.

Reaction Rate: The speed at which reactants are converted into products.
Catalysts: Substances that increase reaction rates without being consumed.
Chemical Equilibrium: The state where the rate of the forward reaction equals the rate of the reverse reaction.

Hydrocarbons: Organic compounds made of hydrogen and carbon; can be saturated (alkanes) or unsaturated (alkenes, alkynes).
Functional Groups: Specific groupings of atoms that determine the properties of organic compounds (e.g., alcohols, carboxylic acids).
Isomerism: Compounds with the same molecular formula but different structural arrangements.

Matter is defined as anything that possesses mass and occupies physical space; it exists in three main states: solid, liquid, and gas.
Atoms are the fundamental building blocks of matter, composed of protons (positive), neutrons (neutral), and electrons (negative).
Elements are pure substances consisting of a single type of atom, which are organized in the periodic table.

The nucleus is the atom's core, housing protons and neutrons.
Electrons orbit around the nucleus in designated electron shells, contributing to an atom's overall charge.
The atomic number indicates the quantity of protons in an atom and characterizes the specific element.
Mass number is the sum of protons and neutrons within an atom, reflecting its overall weight.

Ionic bonds occur through the transfer of electrons between atoms, leading to the formation of charged ions.
Covalent bonds are established when two atoms share pairs of electrons.
Metallic bonds are found between metal atoms, where electrons are pooled in a 'sea,' permitting shared movement.

Reactants are the starting substances that undergo transformation during a chemical reaction.
Products are the new substances produced by the chemical reaction.
Types of reactions include:
- Synthesis: Multiple reactants combine to form a new compound.
- Decomposition: A single compound disintegrates into simpler substances.
- Single Replacement: An element within a compound is replaced by another single element.
- Double Replacement: Exchange of ions between two reacting compounds occurs.

Solids possess a definite shape and volume with particles tightly packed together.
Liquids have a definite volume but adapt their shape to fit within their container, featuring loosely arranged particles.
Gases exhibit neither a fixed shape nor volume, with particles spaced far apart, allowing high mobility.

Acids are proton donors (releasing H+) in aqueous solutions, characterized by a pH less than 7.
Bases accept protons or donate hydroxide ions (OH-) in solution and have a pH greater than 7.
The pH scale quantifies acidity to basicity, ranging from 0 (highly acidic) to 14 (highly basic).

Elements are categorized into groups (vertical columns) that share similar physical and chemical properties.
Periods (horizontal rows) indicate the sequential energy levels occupied by electrons.
Elements fall into three classifications: metals (good conductors, malleable), nonmetals (poor conductors), and metalloids (exhibit characteristics of both).

A mole is defined as the quantity of substance containing the same number of atoms as 12 grams of carbon-12, approximately 6.022 x 10^23 entities.
Molar mass is the mass of one mole of a substance and is calculated by adding the atomic masses of all its constituent elements.
Chemical equations must be balanced to comply with the law of conservation of mass, reflecting equal mass on both sides of the reaction.

Exothermic reactions release heat energy into the surroundings, often resulting in a temperature increase.
Endothermic reactions absorb heat energy from their surroundings, causing a temperature decrease.
Enthalpy (H) represents the total heat content of a system, crucial for understanding energy changes during reactions.

Reaction rate describes the velocity at which reactants transform into products.
Catalysts are agents that enhance reaction speeds without being consumed in the reaction process.
Chemical equilibrium exists when the forward reaction rate equals the reverse reaction rate, signifying a stable system.

Hydrocarbons are compounds composed solely of hydrogen and carbon; they can be classified as saturated (alkanes) or unsaturated (alkenes, alkynes).
Functional groups are specific atom groupings that impart distinct chemical properties to organic compounds, such as alcohols and carboxylic acids.
Isomerism refers to the phenomenon where compounds share the same molecular formula but differ in structural configuration.