Basic Concepts of Chemistry

Matter
- Anything that has mass and occupies space.
- Exists in three states: solid, liquid, gas.
Elements
- Pure substances that cannot be broken down.
- Each element is defined by the number of protons (atomic number).
- Examples: Hydrogen (H), Carbon (C), Oxygen (O).
Compounds
- Substances formed from two or more elements chemically bonded.
- Have properties different from their constituent elements.
- Examples: Water (H₂O), Sodium Chloride (NaCl).

Atoms
- Basic units of matter.
- Composed of protons, neutrons, and electrons.
Subatomic Particles
- Protons: Positively charged, found in nucleus.
- Neutrons: Neutral charge, found in nucleus.
- Electrons: Negatively charged, orbit nucleus in electron clouds.
Isotopes
- Atoms of the same element with different numbers of neutrons.
- Example: Carbon-12 and Carbon-14.

Ionic Bonds
- Formed when electrons are transferred from one atom to another.
- Results in oppositely charged ions attracting each other.
Covalent Bonds
- Formed when two atoms share one or more pairs of electrons.
- Can be polar (unequal sharing) or nonpolar (equal sharing).
Metallic Bonds
- Involves the sharing of free electrons among a lattice of metal atoms.
- Responsible for properties like conductivity and malleability.

Types of Reactions
- Synthesis: A + B → AB
- Decomposition: AB → A + B
- Single Replacement: A + BC → AC + B
- Double Replacement: AB + CD → AD + CB
- Combustion: Hydrocarbon + O₂ → CO₂ + H₂O
Balancing Reactions
- Law of Conservation of Mass: Mass is neither created nor destroyed.
- Each side of a reaction must have the same number of atoms for each element.

Organization
- Elements are arranged by increasing atomic number.
- Groups (columns) share similar chemical properties.
- Periods (rows) indicate energy levels of electrons.
Key Groups
- Alkali Metals (Group 1): Highly reactive, soft metals.
- Alkaline Earth Metals (Group 2): Reactive metals, higher melting points.
- Transition Metals: D-block elements, often form colorful compounds.
- Halogens (Group 17): Very reactive nonmetals.
- Noble Gases (Group 18): Inert gases, complete outer electron shells.

Acids
- Substances that donate protons (H⁺ ions).
- Have a sour taste and turn blue litmus paper red.
- Examples: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄).
Bases
- Substances that accept protons or donate hydroxide ions (OH⁻).
- Have a bitter taste and turn red litmus paper blue.
- Examples: Sodium hydroxide (NaOH), Ammonia (NH₃).
pH Scale
- Measures the acidity or basicity of a solution.
- Ranges from 0 (strongly acidic) to 14 (strongly basic); 7 is neutral.

Law of Thermodynamics
- First Law: Energy cannot be created or destroyed, only transformed.
- Second Law: Entropy of an isolated system always increases.
Endothermic and Exothermic Reactions
- Endothermic: Absorb heat (e.g., photosynthesis).
- Exothermic: Release heat (e.g., combustion).

Hydrocarbons
- Compounds consisting entirely of hydrogen and carbon.
- Types: Alkanes (single bonds), Alkenes (double bonds), Alkynes (triple bonds).
Functional Groups
- Specific groupings of atoms that impart characteristics to molecules.
- Common groups: Hydroxyl (-OH), Carboxyl (-COOH), Amino (-NH₂).

Coordination Compounds
- Composed of a central metal atom bonded to surrounding molecules or ions (ligands).
Transition Metals
- Elements with incomplete d-subshells, known for variable oxidation states and complex ion formation.

Chemistry is the study of matter, its properties, and the changes it undergoes.
Understanding the basic principles of chemistry is crucial for delving into more complex concepts and applications in science and industry.

Matter is defined as anything with mass that occupies space, presented in three states: solid, liquid, and gas.
Elements are pure substances characterized by their atomic number, which indicates the number of protons; notable examples include Hydrogen (H), Carbon (C), and Oxygen (O).
Compounds arise from two or more elements chemically bonded, displaying properties distinct from their individual elements, such as Water (H₂O) and Sodium Chloride (NaCl).

Atoms serve as the fundamental building blocks of matter, composed of protons, neutrons, and electrons.
Subatomic particles include protons (positive charge, located in the nucleus), neutrons (neutral charge, also in the nucleus), and electrons (negative charge, orbiting the nucleus).
Isotopes are variations of the same element possessing differing neutron numbers, illustrating this with Carbon-12 and Carbon-14.

Ionic bonds result from the transfer of electrons between atoms, leading to the formation of oppositely charged ions that attract each other.
Covalent bonds involve the sharing of electron pairs between atoms, classified as polar (unequal sharing) or nonpolar (equal sharing).
Metallic bonds occur when free electrons are shared among a lattice of metal atoms, contributing to properties like electrical conductivity and malleability.

Types of chemical reactions include synthesis (A + B → AB), decomposition (AB → A + B), single replacement (A + BC → AC + B), double replacement (AB + CD → AD + CB), and combustion (Hydrocarbon + O₂ → CO₂ + H₂O).
Balancing chemical reactions adheres to the Law of Conservation of Mass, ensuring atom counts for each element are equal on both sides.

The periodic table organizes elements by ascending atomic number, with groups (columns) displaying similar chemical properties and periods (rows) indicating levels of electron energy.
Key groups in the table include Alkali Metals (very reactive), Alkaline Earth Metals (reactive, with high melting points), Transition Metals (form colorful compounds), Halogens (highly reactive nonmetals), and Noble Gases (inert with complete outer electron shells).

Acids are substances that donate protons (H⁺ ions), recognized for their sour taste and ability to turn blue litmus paper red, with examples like Hydrochloric acid (HCl) and Sulfuric acid (H₂SO₄).
Bases accept protons or donate hydroxide ions (OH⁻), typically tasting bitter and turning red litmus paper blue, such as Sodium hydroxide (NaOH) and Ammonia (NH₃).
The pH scale quantifies acidity and basicity, ranging from 0 (strongly acidic) to 14 (strongly basic), with 7 being neutral.

The First Law of Thermodynamics states energy cannot be created or destroyed, only transformed, while the Second Law asserts that the entropy of an isolated system always increases.
Endothermic reactions absorb heat (example: photosynthesis), whereas exothermic reactions release heat (example: combustion).

Hydrocarbons are compounds composed solely of hydrogen and carbon, differentiated into types: Alkanes (single bonds), Alkenes (double bonds), and Alkynes (triple bonds).
Functional groups are specific clusters of atoms determining the chemical properties of molecules, with common examples being Hydroxyl (-OH), Carboxyl (-COOH), and Amino (-NH₂).

Coordination compounds feature a central metal atom bonded to surrounding ligands (molecules or ions).
Transition metals are known for their incomplete d-subshells, which lead to variability in oxidation states and the formation of complex ions.

Chemistry encompasses the study of matter, its properties, and changes, forming a foundational understanding crucial for exploring advanced scientific concepts and applications.