Atomic Structure and Chemical Laws Explained

Atomic Structure Concepts

Balmer Series

The striped visible emission spectrum of H corresponds to the transitions of excited electrons returning to level n = 2.

Lyman Series

If electrons transition to level n = 1, the energy differences are greater, resulting in higher frequencies. The lines of this spectrum appear in the ultraviolet region.

Quantum Model and Orbitals

Quantum Model

An electron with a given energy sublevel occupies a defined region of space called an orbital.

Orbital Definition

An orbital is a region of space where there is a high probability of finding the electron.

Form of an Orbital

The form of an orbital depends on the type of sublevel (q) it belongs to. S orbitals are spherical; P orbitals are dumbbell-shaped (often described as 'weights' or lobes).

Orbital Size

Orbital size depends on the value of the principal quantum number (n).

Electronic Configuration

Electronic configuration is the distribution of electrons in an atom across different sublevels and orbitals.

Principles Governing Configuration

• Aufbau Principle: In a ground-state atom, electrons occupy the lowest energy orbitals available first.
• Pauli Exclusion Principle: Each orbital can fit only two electrons, and they must have opposite spins.
• Hund's Rule: When several electrons occupy orbitals of the same energy (i.e., the same sublevel), they are arranged to maximize the number of unpaired electrons.

Foundational Chemical Theories

Hypotheses of Dalton's Theory

• Simple substances (elements) are formed by a single type of tiny, indivisible particles called atoms.
• All atoms of a chemical element are identical in mass and other properties.
• Atoms of different chemical elements have different masses.
• Compounds are formed when atoms of different elements combine, forming "compound atoms" (molecules).

Chemical Laws

Law of Conservation of Mass (LCM) - Lavoisier

The mass of the products of a chemical reaction is always equal to the mass of the reactants. This is explained because a chemical change is just a rearrangement of atoms; atoms are not created or destroyed. Atoms are unchangeable units.

Law of Definite Proportions (LDP) - Proust

The elements that combine to form a compound always do so in the same mass ratio. This is explained by the fact that the ratio of the masses of the elements combined is the same as the ratio between the masses of the constituent atoms or molecules that react.