Basic Concepts of Chemistry

Matter: Anything that has mass and takes up space; exists in three states: solid, liquid, gas.
Atoms: The basic unit of matter; consist of protons, neutrons, and electrons.
Elements: Pure substances that cannot be broken down; represented by symbols (e.g., H for hydrogen, O for oxygen).
Compounds: Substances formed from two or more elements chemically bonded (e.g., H2O).

Structure: Organized by increasing atomic number; elements are grouped based on similar properties.
Groups/Families: Vertical columns; elements in the same group share chemical properties (e.g., alkali metals, noble gases).
Periods: Horizontal rows; properties change progressively across periods.

Ionic Bonds: Formed through the transfer of electrons between atoms, resulting in charged ions (e.g., NaCl).
Covalent Bonds: Formed by the sharing of electrons between atoms (e.g., H2O).
Metallic Bonds: Characterized by a sea of delocalized electrons shared among metal atoms.

Types of Reactions:
- Synthesis: Two or more substances combine to form one product (A + B → AB).
- Decomposition: A single compound breaks down into two or more products (AB → A + B).
- Single Replacement: One element replaces another in a compound (A + BC → AC + B).
- Double Replacement: Exchange of ions between two compounds (AB + CD → AD + CB).
- Combustion: Reaction with oxygen producing energy, carbon dioxide, and water (e.g., hydrocarbon + O2 → CO2 + H2O).

Acids: Substances that donate protons (H+) in a solution; characterized by a sour taste and pH < 7 (e.g., HCl).
Bases: Substances that accept protons or donate hydroxide ions (OH-); characterized by a bitter taste and pH > 7 (e.g., NaOH).
pH Scale: Ranges from 0 to 14; pH < 7 is acidic, pH = 7 is neutral, pH > 7 is basic.

Mole Concept: A mole is 6.022 x 10^23 particles (Avogadro's number); used for counting atoms, molecules, and formula units.
Balancing Equations: Ensures that the number of atoms of each element is the same on both sides of a chemical equation.

Endothermic Reactions: Absorb heat from the surroundings (e.g., photosynthesis).
Exothermic Reactions: Release heat to the surroundings (e.g., combustion of fuels).

Solvent: The substance that dissolves the solute (e.g., water).
Solute: The substance that is dissolved (e.g., salt in water).
Concentration: Measure of the amount of solute in a given volume of solvent (e.g., molarity).

Hydrocarbons: Compounds consisting solely of hydrogen and carbon; classified as alkanes, alkenes, and alkynes based on bonding.
Functional Groups: Specific groups of atoms within molecules that determine chemical reactivity (e.g., hydroxyl -OH, carboxyl -COOH).

Coordination Compounds: Complexes formed by transition metals bonded to ligands.
Salts: Ionic compounds formed by the neutralization reaction of acids and bases.

Reaction Rate: The speed at which reactants are converted to products; influenced by concentration, temperature, and catalysts.
Catalysts: Substances that increase the rate of a reaction without being consumed.

Dynamic Equilibrium: The state in which the forward and reverse reactions occur at the same rate; concentrations of reactants and products remain constant.
Le Chatelier's Principle: If a system at equilibrium is subjected to change, the system will shift in a direction that counteracts the change.

Matter includes anything with mass that occupies space; its three primary states are solid, liquid, and gas.
Atoms represent the fundamental units of matter, composed of protons, neutrons, and electrons.
Elements are pure substances that cannot be decomposed; each is identified by unique chemical symbols, like H for hydrogen and O for oxygen.
Compounds consist of two or more elements united by chemical bonds, such as water (H2O).

Elements in the periodic table are arranged according to increasing atomic number and grouped by similar properties.
Groups or families are vertical columns where elements share common chemical characteristics, such as alkali metals and noble gases.
Periods are horizontal rows that exhibit gradual changes in properties across the table.

Ionic bonds occur through electron transfer between atoms, resulting in positively and negatively charged ions (e.g., sodium chloride - NaCl).
Covalent bonds involve the sharing of electrons between atoms (e.g., water - H2O).
Metallic bonds exist between metal atoms, characterized by a collective sea of delocalized electrons.

Synthesis reactions combine two or more reactants to produce a single product (e.g., A + B → AB).
Decomposition reactions involve breaking down a single compound into two or more products (e.g., AB → A + B).
Single replacement reactions have one element displacing another in a compound (e.g., A + BC → AC + B).
Double replacement reactions are characterized by the exchange of ions between two compounds (e.g., AB + CD → AD + CB).
Combustion reactions with oxygen yield energy, carbon dioxide, and water, often involving hydrocarbons (e.g., hydrocarbon + O2 → CO2 + H2O).

Acids are substances that donate protons (H+) in solution, typically sour tasting, with a pH less than 7 (e.g., hydrochloric acid - HCl).
Bases are substances that accept protons or release hydroxide ions (OH-), generally bitter tasting, with a pH greater than 7 (e.g., sodium hydroxide - NaOH).
The pH scale ranges from 0 to 14, indicating acidity (pH < 7), neutrality (pH = 7), and basicity (pH > 7).

A mole is a counting unit equivalent to 6.022 x 10^23 particles, useful for quantifying atoms, molecules, or formula units.
Balancing chemical equations ensures that the number of atoms for each element remains constant on both sides.

Endothermic reactions absorb heat from their surroundings; an example is photosynthesis.
Exothermic reactions release heat, such as the combustion of fuels.

Solvents are the liquid components that dissolve solutes, exemplified by water.
Solutes are the substances being dissolved, like salt in water.
Concentration quantifies the amount of solute in a specific volume of solvent, commonly measured as molarity.

Hydrocarbons are molecules made entirely of hydrogen and carbon, categorized into alkanes, alkenes, and alkynes based on bonding types.
Functional groups are specific atom groups in molecules that dictate chemical reactivity, such as hydroxyl (-OH) and carboxyl (-COOH) groups.

Coordination compounds consist of transition metals bonded to ligands, forming complex structures.
Salts are ionic compounds resulting from the neutralization reaction between acids and bases.

Reaction rate indicates how quickly reactants transform into products, affected by factors like concentration, temperature, and the presence of catalysts.
Catalysts enhance reaction rates without undergoing permanent changes themselves.

Dynamic equilibrium describes a state where forward and reverse reactions proceed at equal rates, keeping reactant and product concentrations stable.
According to Le Chatelier's Principle, if an equilibrium system experiences a change, it will adjust to counteract that change and restore balance.