Compostos i Elements Químics

Chemical Compounds and Elements

• A compound is formed when two or more elements from the periodic table bond together. These can be broken down into simpler substances through chemical reactions.
• Examples include water (H₂O), which can be separated into hydrogen and oxygen through electrolysis.
• Atoms in compounds and elements are held together by chemical bonds.

Chemical Elements

• A chemical element is a type of matter composed of atoms with identical properties.
• Atoms have a nucleus containing protons and neutrons, and electrons orbiting the nucleus.
• Each element has a unique number of protons called the atomic number.
• Elements cannot be broken down chemically.
• Atoms of the same element can have different numbers of neutrons, forming isotopes. Isotopes have the same number of protons but different mass numbers.

Properties of Chemical Elements

• Scientists have organized elements based on their chemical properties.
• The periodic table is a way of classifying elements based on their properties, evolving over time as more elements are discovered.
• Early classification systems were based on atomic mass.

Atoms and Their Properties

• Democritus (400 BCE) proposed that matter is made up of indivisible particles called atoms.
• Dalton (1808) refined this with his atomic theory, which suggests important concepts about atoms including:
  • Matter is composed of indivisible atoms.
  • All atoms of the same element are identical in mass and chemical properties.
  • Different elements have different kinds of atoms
  • Atoms combine to form compounds. The ratios of atoms in a compound are whole numbers. Reactants are broken down and rearranged
• Thomson's model proposed a "plum pudding" model, a sphere of positive charge with negatively charged electrons embedded within.
• Rutherford's model suggested a small dense positively charged nucleus with electrons orbiting it.
• Bohr's model described electrons orbiting the nucleus in specific energy levels.
• The quantum mechanical model depicts electrons as existing in orbitals, regions of space where there's a high probability of finding electrons.

Dalton's Atomic Model

• Tenet 1: Atoms are indivisible and unchangeable.
• Tenet 2: Atoms of the same element are identical in mass and properties, and different from atoms of other elements.
• Tenet 3: Compounds are formed when atoms from different elements combine in whole-number ratios.
• Tenet 4: Atoms are exchanged during chemical reactions, but none are created or destroyed.

Thomson's Atomic Model

• Thomson's model suggested a sphere of positive charge with negatively-charged electrons embedded within.

Rutherford's Atomic Model

• Rutherford's model proposed a dense, positively charged nucleus at the center of the atom, with electrons orbiting around it.

Bohr's Atomic Model

• Bohr's model suggested that electrons orbit the nucleus in specific energy levels.

Quantum Mechanical Model

• Electrons exist in orbitals, areas of space where there's a high probability of finding them.
• The quantum mechanical model is based on mathematical equations, describing the behavior of electrons.
• Quantum numbers (principal, azimuthal, magnetic, and spin) define the electron's properties in the model

Atomic Number and Mass Number

• The atomic number (Z) is the number of protons in an atom's nucleus.
• The mass number (A) is the sum of protons and neutrons in an atom's nucleus.
• Isotopes are atoms of the same element with different numbers of neutrons (same atomic number but different mass numbers).

Atomic Mass

• Atomic mass is the weighted average of the masses of all the isotopes of an element, taking into account their relative abundances.

Electron Configuration

• Electrons fill orbitals and energy levels based on increasing energy levels and certain rules.
• Electron Configurations represent the arrangement of electrons in atomic orbitals.

Explora les propietats i estructures dels compostos i elements químics. Descobreix com es formen, les seves característiques i la seva organització en la taula periòdica. Aquest qüestionari et desafiarà amb preguntes sobre estructures atòmiques i reaccions químiques.