Chem Basic Principles and Conceptual Topics

Gen Chem 1 & 2

Aufbau Principle

Electrons fill the lowest energy orbitals first.

Hund's Rule

Electrons pair up in orbitals only after every orbital in a subshell has one electron.

Pauli Exclusion

No two electrons can have the exact same four quantum numbers.

VSEPR Theory

Valence Shell Electron Pair Repulsion. Electron pairs push apart to maximize distance, dictating molecular shape.

Ideal Gas Behavior

Molecules have no volume and zero intermolecular attractions (PV = nRT).

Coulomb’s Law

The force between two charged particles increases with larger charges and decreases as the distance between them increases.

Dalton’s Law of Partial Pressures

The total pressure of a mixture of non-reacting gases is equal to the sum of the individual pressures exerted by each gas alone. (P_total= P_A+ P_B+ P_C )

IMF Hierarchy

Forces between molecules. London Dispersion (weakest, all molecules) < Dipole-Dipole < Hydrogen Bonding (strongest neutral IMF, requires H bound to N, O, or F).

Stronger IMFs lead to ____ boiling points, ____ surface tension, and ____ vapor pressure.

Higher; higher; lower

Catalysts

Speed up reactions by providing an alternate pathway with a lower activation energy. They are not consumed.

Equilibrium Constant (K)

Ratio of products to reactants.

(K > 1)

Products are favored.

(K < 1)

Reactants are favored.

Le Chatelier’s Principle

If a system at equilibrium is disturbed, it will shift its position to counteract the stress.

Arrhenius

Acids yield (H⁺); Bases yield (OH^-).

Brønsted-Lowry

Acids donate protons (H⁺); Bases accept protons.

Buffers

Solutions made of a weak acid/base pair that resist changes in pH when small amounts of acid or base are added.

Reduction

Gaining electrons.

Oxidation

Losing electrons.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed from one form to another. The total energy of the universe is constant.

Second Law of Thermodynamics

In any spontaneous process, the total entropy (disorder) of the universe always increases.

Third Law of Thermodynamics

The entropy of a pure, perfectly crystalline substance is exactly zero at absolute zero temperature (0 ^oK).