Basic Concepts of Chemistry

Basic Concepts of Chemistry

• Matter: Anything that has mass and occupies space.
• Elements: Pure substances that cannot be broken down into simpler substances (e.g., hydrogen, oxygen).
• Compounds: Substances formed when two or more elements chemically bond (e.g., water - H₂O).
• Mixtures: Combinations of two or more substances that are not chemically bonded (e.g., air, salad).

Atomic Structure

• Atom: The basic unit of matter, composed of protons, neutrons, and electrons.
  • Protons: Positively charged particles found in the nucleus.
  • Neutrons: Neutral particles also found in the nucleus.
  • Electrons: Negatively charged particles that orbit the nucleus.
• Atomic Number: The number of protons in an atom's nucleus; defines the element.
• Mass Number: The total number of protons and neutrons in an atom.

Chemical Bonding

• Ionic Bonds: Formed when electrons are transferred from one atom to another (e.g., NaCl).
• Covalent Bonds: Formed when two atoms share electrons (e.g., O₂).
• Metallic Bonds: Occur between metal atoms where electrons are shared in a 'sea' of electrons.

Chemical Reactions

• Reactants: Substances that undergo change in a chemical reaction.
• Products: New substances formed as a result of a chemical reaction.
• Types of Reactions:
  • Synthesis: Two or more reactants combine to form a single product (A + B → AB).
  • Decomposition: A single compound breaks down into two or more products (AB → A + B).
  • Single Replacement: An element replaces another in a compound (A + BC → AC + B).
  • Double Replacement: Exchange of ions between two compounds (AB + CD → AD + CB).
  • Combustion: A substance reacts with oxygen, releasing energy (usually involves hydrocarbons).

The Periodic Table

• Groups/Families: Vertical columns that contain elements with similar properties (e.g., alkali metals, halogens).
• Periods: Horizontal rows that represent energy levels of electrons.
• Metals, Nonmetals, and Metalloids:
  • Metals: Good conductors, malleable, ductile (e.g., iron, gold).
  • Nonmetals: Poor conductors, brittle, diverse properties (e.g., carbon, nitrogen).
  • Metalloids: Have properties of both metals and nonmetals (e.g., silicon, arsenic).

Acids and Bases

• Acids: Substances that donate protons (H⁺ ions) in solution (e.g., hydrochloric acid - HCl).
• Bases: Substances that accept protons or donate hydroxide ions (OH⁻) in solution (e.g., sodium hydroxide - NaOH).
• pH Scale: Measures the acidity or basicity of a solution:
  • pH < 7: Acidic
  • pH = 7: Neutral
  • pH > 7: Basic

Stoichiometry

• Mole: A unit that measures the amount of substance, equivalent to Avogadro's number (6.022 x 10²³ particles).
• Molar Mass: The mass of one mole of a substance (g/mol) calculated using the periodic table.
• Balanced Chemical Equations: Equations must have the same number of atoms of each element on both sides to obey the law of conservation of mass.

Thermodynamics in Chemistry

• Exothermic Reactions: Release heat (e.g., combustion).
• Endothermic Reactions: Absorb heat (e.g., photosynthesis).
• Enthalpy (ΔH): The heat content of a system.

Kinetics and Equilibrium

• Reaction Rate: The speed at which reactants are converted to products, affected by:
  • Concentration
  • Temperature
  • Surface area
  • Catalysts
• Chemical Equilibrium: The state where the rate of the forward reaction equals the rate of the reverse reaction.

Organic Chemistry

• Hydrocarbons: Compounds composed of hydrogen and carbon (e.g., alkanes, alkenes, alkynes).
• Functional Groups: Specific groups of atoms that impart characteristic properties to organic compounds (e.g., hydroxyl -OH, carboxyl -COOH).

These notes cover the fundamental concepts and categories within chemistry, providing a solid foundation for further study.

Basic Concepts of Chemistry

• Matter has mass and occupies space; it constitutes everything around us.
• Elements cannot be broken down into simpler substances and include foundational elements like hydrogen and oxygen.
• Compounds are formed from the chemical bonding of two or more elements (e.g., water is H₂O).
• Mixtures are combinations of substances that retain their individual properties and can be physically separated (e.g., air and salad).

Atomic Structure

• An atom is the smallest unit of matter, comprising protons, neutrons, and electrons.
• Protons are positively charged particles located in the nucleus of the atom.
• Neutrons are neutral particles found alongside protons in the nucleus.
• Electrons are negatively charged particles that orbit the nucleus and are involved in chemical bonding.
• The atomic number specifies the number of protons in an atom, determining the element's identity.
• The mass number equals the total count of protons and neutrons in an atom.

Chemical Bonding

• Ionic bonds arise when electrons are transferred between atoms, resulting in charged ions (e.g., sodium chloride or NaCl).
• Covalent bonds form through the sharing of electrons between two atoms (e.g., molecular oxygen or O₂).
• Metallic bonds occur among metal atoms, characterized by a 'sea' of delocalized electrons facilitating conductivity.

Chemical Reactions

• Reactants are the initial substances that undergo change during a reaction.
• Products are the new substances formed as a result of the chemical transformation.
• Types of reactions include:
  • Synthesis: Two or more reactants form a single product (A + B → AB).
  • Decomposition: A single compound breaks down into two or more products (AB → A + B).
  • Single Replacement: An element in a compound is replaced by another element (A + BC → AC + B).
  • Double Replacement: Ions from two compounds exchange places (AB + CD → AD + CB).
  • Combustion: Involves a substance reacting with oxygen, often producing energy, typically involving hydrocarbons.

The Periodic Table

• Groups or families are vertical columns that encompass elements with similar chemical properties (e.g., alkali metals, halogens).
• Periods are horizontal rows representing energy levels of electrons surrounding the nucleus.
• Metals exhibit good electrical conductivity, malleability, and ductility (e.g., iron, gold).
• Nonmetals are generally poor conductors and can be brittle with diverse physical properties (e.g., carbon, nitrogen).
• Metalloids possess a blend of properties from both metals and nonmetals (e.g., silicon, arsenic).

Acids and Bases

• Acids donate protons (H⁺ ions) in solutions (e.g., hydrochloric acid - HCl).
• Bases accept protons or donate hydroxide ions (OH⁻) in solutions (e.g., sodium hydroxide - NaOH).
• The pH scale quantifies acidity or basicity:
  • pH < 7 indicates an acidic solution.
  • pH = 7 represents a neutral solution.
  • pH > 7 denotes a basic solution.

Stoichiometry

• A mole quantifies an amount of substance, equivalent to Avogadro's number (approximately 6.022 x 10²³ particles).
• Molar mass indicates the mass of one mole of a substance (expressed in grams per mole, g/mol) and is determined using the periodic table.
• Balanced chemical equations obey the law of conservation of mass, ensuring equal atom counts on both sides of the equation.

Thermodynamics in Chemistry

• Exothermic reactions release heat into the surroundings (e.g., combustion).
• Endothermic reactions absorb heat from the surroundings (e.g., photosynthesis).
• Enthalpy (ΔH) refers to the total heat content within a system, influencing energy changes during reactions.

Kinetics and Equilibrium

• Reaction rate measures how quickly reactants are converted into products, influenced by factors such as concentration, temperature, surface area, and the presence of catalysts.
• Chemical equilibrium exists when the rate of the forward reaction equals the rate of the reverse reaction, achieving a stable state in the reaction mixture.

Organic Chemistry

• Hydrocarbons consist solely of carbon and hydrogen atoms and can be categorized into alkanes, alkenes, and alkynes.
• Functional groups are specific atom arrangements in organic compounds that confer distinct chemical properties (e.g., hydroxyl -OH, carboxyl -COOH).