Basic Concepts in Chemistry

Matter: Anything that has mass and occupies space. Divided into:
- Elements: Pure substances that cannot be broken down.
- Compounds: Substances formed from two or more elements chemically bonded.
Atoms: The basic unit of a chemical element. Consist of:
- Protons: Positively charged particles in the nucleus.
- Neutrons: Neutral particles in the nucleus.
- Electrons: Negatively charged particles orbiting the nucleus.
Molecules: Two or more atoms bonded together, can be the same or different elements.

Organized by increasing atomic number.
Groups (columns) represent elements with similar properties.
Periods (rows) indicate the number of electron shells.
Key groups:
- Alkali metals: Group 1, highly reactive.
- Alkaline earth metals: Group 2, also reactive, but less than Group 1.
- Noble gases: Group 18, inert, non-reactive due to having a full valence shell.

Ionic bonds: Formed when electrons are transferred from one atom to another, creating charged ions.
Covalent bonds: Formed when two atoms share electrons.
Metallic bonds: A bond found in metals, where electrons are shared in a "sea" of electrons, allowing conductivity.

Reactants: Substances that undergo change during a reaction.
Products: Substances formed as a result of a chemical reaction.
Types of reactions:
- Synthesis: Two or more reactants combine to form a product.
- Decomposition: A single compound breaks down into two or more products.
- Single replacement: One element replaces another in a compound.
- Double replacement: Exchange of ions between two compounds.
- Combustion: A substance combines with oxygen, releasing energy.

Acids: Substances that donate protons (H+ ions).
- Properties: Sour taste, turns blue litmus paper red.
Bases: Substances that accept protons or release hydroxide ions (OH-).
- Properties: Bitter taste, slippery feel, turns red litmus paper blue.
pH scale: Measures acidity or alkalinity; ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

Solid: Definite shape and volume, particles are closely packed.
Liquid: Definite volume but no definite shape, particles are close but can move freely.
Gas: No definite shape or volume, particles are far apart and move freely.
Plasma: High energy state of matter with ionized gases.

Solution: A homogeneous mixture of solute and solvent.
Solvent: The substance that dissolves the solute.
Solute: The substance that is dissolved.
Concentration: Amount of solute in a given volume of solvent; can be expressed in molarity (moles per liter).

Reaction rates: Speed at which a reaction occurs, influenced by factors like temperature, concentration, surface area, and catalysts.
Equilibrium: The state in which the forward and reverse reactions occur at the same rate.

These notes provide a concise overview of foundational concepts in chemistry necessary for further study.

Anything that has mass and occupies space.
Divided into three categories:
- Elements: Pure substances that cannot be broken down further.
- Compounds: Substances formed from two or more elements chemically bonded together.
- Mixtures: Combinations of substances that can be separated by physical means.

The fundamental building block of all matter.
Composed of three subatomic particles:
- Protons: Positively charged particles located in the nucleus.
- Neutrons: Neutral particles located in the nucleus.
- Electrons: Negatively charged particles orbiting the nucleus in shells.

Alkali Metals: Group 1, highly reactive due to having one valence (outermost) electron.
Alkaline Earth Metals: Group 2, reactive but less so than alkali metals.
Halogens: Group 17, highly reactive nonmetals that form salts with metals.
Noble Gases: Group 18, inert (non-reactive) due to having a full valence shell.

The forces that hold atoms together in molecules and compounds.
Types of chemical bonds:
- Ionic Bonds: Formed by the transfer of electrons, creating oppositely charged ions that attract each other.
- Covalent Bonds: Formed by the sharing of electrons between atoms.
- Metallic Bonds: Occur in metals, where electrons are shared in a "sea" of electrons, contributing to their conductivity.

Processes involving the rearrangement of atoms and molecules.
Key terms:
- Reactants: Substances that undergo change during a reaction.
- Products: Substances formed as a result of a chemical reaction.

Synthesis: Two or more reactants combine to form a single product.
Decomposition: A single reactant breaks down into two or more products.
Single Replacement: One element replaces another in a compound.
Double Replacement: Exchange of ions between two compounds.
Combustion: A rapid reaction involving a substance combining with oxygen, releasing energy (heat and light).

Acids: Substances that donate hydrogen ions (H+) in solution.
Bases: Substances that accept hydrogen ions or release hydroxide ions (OH-) in solution.
pH Scale: Measures the acidity or alkalinity of a solution.
- Ranges from 0 (most acidic) to 14 (most basic).
- 7 is neutral.

The physical forms in which matter exists.
- Solid: Definite shape and volume, tightly packed particles.
- Liquid: Definite volume but no definite shape, particles are close but can move freely.
- Gas: No definite shape or volume, particles are far apart and move freely.
- Plasma: Ionized gas with a high energy state.

The study of heat changes in chemical reactions.
Types of Reactions:
- Endothermic reactions: Absorb heat from the surroundings.
- Exothermic reactions: Release heat to the surroundings.

Reaction Rates: The speed at which a chemical reaction occurs.
Equilibrium: A state where the rates of the forward and reverse reaction are equal, resulting in no net change in concentration of reactants and products.