Naturaleza de la Materia y sus Propiedades

1.1 Enlace químico, periodicidad y relación con propiedades

Understanding the nature of matter and its properties is fundamental in General Chemistry. This topic covers the classification of matter, its physical and chemical properties, and the atomic theory that explains the structure and transformation of substances.

Sustancias puras y mezclas

All matter can be classified as either pure substances or mixtures. This classification is essential for understanding chemical behavior and separation techniques.

• Sustancias puras: These have a fixed composition and distinct properties. They are further divided into:

  • Elementos: Substances made of only one type of atom. Examples: Oxygen (O2), Copper (Cu), Silver (Ag), Iron (Fe).

  • Compuestos: Substances composed of two or more different atoms chemically bonded. Examples: Water (H2O), Salt (NaCl), Ammonia (NH3), Carbon dioxide (CO2).

• Mezclas: Combinations of two or more substances where each retains its own properties. They are classified as:

  • Mezclas homogéneas: Uniform composition throughout. Examples: Sugar dissolved in water, coffee, steel.

  • Mezclas heterogéneas: Non-uniform composition. Examples: Raisin bread, granite, marble.

Propiedades de las sustancias

• Físicas: Properties that can be observed or measured without changing the substance's identity (e.g., melting point, density).

• Químicas: Properties that describe a substance's ability to undergo chemical changes (e.g., reactivity, flammability).

• Intensivas: Do not depend on the amount of substance (e.g., density, boiling point).

• Extensivas: Depend on the amount of substance (e.g., mass, volume).

Átomo y teoría atómica

The atomic theory explains the composition of matter at the smallest scale. All matter is made up of atoms, which are the basic units of elements.

• Átomo: The smallest unit of an element that retains its chemical properties.

• Each element consists of a unique type of atom.

• Atoms combine to form compounds.

Ejemplo: Teoría atómica de Dalton

• All elements are composed of tiny, indivisible particles called átomos.

• Atoms of the same element are iguales (identical), but diferentes from those of other elements.

• Atoms of different elements combine to form compuestos (compounds) in fixed, whole-number ratios.

• If the same elements form more than one compound, they do so in different, but definite, whole-number ratios.

• Chemical reactions involve the rearrangement of atoms, not their destruction or creation.

Partículas subatómicas

Atoms are composed of subatomic particles: electrons, protons, and neutrons. Their properties determine the behavior of atoms and elements.

• Electrones (e-): Negatively charged particles found in energy levels around the nucleus. Masa: g Carga: C

• Protones (p+): Positively charged particles in the nucleus. Masa: g Carga: C

• Neutrones (n): Neutral particles in the nucleus. Masa: g Carga: 0

Números característicos

• Número másico (A): Total number of protons and neutrons in the nucleus.

• Número atómico (Z): Number of protons in the nucleus (also equals the number of electrons in a neutral atom).

Modelos recientes

• Modern atomic theory includes other subatomic particles such as quarks, mesons, photons, neutrinos, and bosons, which are relevant in advanced physics and chemistry.

Example: Hydrogen Atom

• Protium: (1 proton, 0 neutrons)

• Deuterium: (1 proton, 1 neutron)

• Tritium: (1 proton, 2 neutrons)

Additional info: These notes cover the foundational concepts of matter, atomic structure, and the classification of substances, which are essential for further study in General Chemistry.