Foundational Chemistry: Atoms, Periodic Table, & Key Laws

Fundamental Chemistry Concepts

Atomic Structure & Quantum Numbers

• The mass of a proton is approximately 1 amu (atomic mass unit).
• Quantum Numbers and their values:
  • n (principal quantum number): 1, 2, 3... (up to n)
  • l (azimuthal/angular momentum quantum number): 0, 1, 2... (n-1) for each n
  • m (magnetic quantum number): from -l to +l, including 0, for each l
  • s (spin quantum number): +1/2 and -1/2 for each m

History of the Periodic System

• The "father" of the periodic system, Dmitri Mendeleev, based his arrangement on atomic masses.
• Henry Moseley ordered the current periodic system based on atomic numbers.
• Döbereiner and Newlands' Contributions to the formation of the periodic system:
  1. Döbereiner's Triads: Based on the relationship between atomic mass and chemical behavior. He observed groups of three elements (triads) where the atomic mass of the middle element was approximately the average of the other two.
  2. Newlands' Law of Octaves: Arranged elements by increasing atomic mass in groups of seven. He noted that the eighth element had properties similar to the first.

Key Chemical Definitions

Ionization Energy

The minimum energy required to remove an electron from a gaseous atom, forming a cation.

Atomic Volume

The volume occupied by one mole of atoms, calculated by dividing the atomic mass by its density.

Electron Affinity

The energy released when a gaseous atom captures an electron to form a negative ion (anion).

Electronegativity

The tendency of an atom to attract a shared pair of electrons in a chemical bond.

Ionic Valence

The number of electrons an atom gains or loses to form a stable ion.

Metal

An element that readily loses electrons.

Non-metal

An element that readily gains electrons.

Stationary Orbital

An orbital that does not absorb or emit energy.

Atomic Number (Z)

The number of protons in an atom, which is characteristic for each element.

Mass Number (A)

The sum of protons and neutrons in an atom.

Isotopes

Atoms of the same element (same atomic number/protons) but with different numbers of neutrons, resulting in different mass numbers. Examples include hydrogen's isotopes: protium, deuterium, and tritium.

Fundamental Laws of Chemistry

Laws of Mass Relationships

• Law of Conservation of Mass (Antoine Lavoisier): Mass is neither created nor destroyed; it is only transformed during a chemical reaction.
• Law of Definite Proportions (Joseph Proust): When two or more elements combine to form a specific compound, they always do so in fixed and constant mass proportions.
• Law of Multiple Proportions (John Dalton): If two elements can combine to form more than one compound, then the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers.
• Law of Reciprocal Proportions (Jeremias Richter): The weights of two different elements that combine separately with a fixed weight of a third element are either the same as or simple multiples of the weights in which they combine with each other.

Volumetric Law

• Gay-Lussac's Law of Combining Volumes (Joseph Louis Gay-Lussac): When gases react, their volumes bear a simple whole-number ratio to one another, and to the volume of any gaseous product, provided all volumes are measured under the same conditions of temperature and pressure.

Avogadro's Hypothesis

1. Equal volumes of different gases, under the same conditions of pressure and temperature, contain an equal number of particles.
2. The ultimate particles of elemental gases are not individual atoms but aggregates of atoms, known as molecules.