Chemistry Basics and Atomic Structure

Atoms and Elements

• Everything is made of atoms.
• Atoms consist of a core (protons and neutrons) and electrons.
• Elements are defined by the number of protons.
• The periodic table lists all elements.

Atomic Structure

• Core: Protons (positive) and neutrons (neutral).
• Electrons orbit in shells; outermost are "valence electrons."
• Quantum mechanics: Atoms don't look like traditional models.
• Periodic table groups elements by valence electrons and periods by shells.

Chemical Behavior

• Elements in the same group have similar behavior.
• Alkali metals: 1 valence electron, shiny, soft.
• Mass increases left to right; more protons, electrons, and neutrons.
• Isotopes: Variants of elements with different neutrons.

Ions

• Neutral atoms: Equal protons and electrons.
• Cations: Positive ions (fewer electrons).
• Anions: Negative ions (more electrons).

Chemical Bonds

• Molecules: Two or more atoms bonded.
• Compounds: Molecules with different elements.
• Lewis-Dot Structures: Represent valence electrons and bonds.
• Full outer electron shells lead to lower energy states.

Types of Bonds

• Covalent Bonds: Sharing electrons; polar and nonpolar.
• Ionic Bonds: Transfer of electrons (e.g., Sodium Chloride).
• Metallic Bonds: Electrons shared among a grid of metal atoms.

Forces and Reactions

• Intermolecular Forces (IMFs): Hydrogen bonds, Van der Waals forces.
• Stoichiometry: Ratio of reactants/products based on conservation of mass.

Reaction Types

• Synthesis, Decomposition, Single/Double Replacement: Aim to lower energy.
• Activation energy is required; catalysts reduce it.

Energy in Reactions

• Enthalpy: Internal energy; exothermic (releases heat) vs. endothermic.
• Gibbs Free Energy: Determines spontaneity (exergonic vs. endergonic).

Quantum Mechanics

• Electrons described by quantum numbers (N, l, ml, ms).
• Electron Configuration: Describes distribution in orbitals.
• Aufbau Principle: Order for filling electron subshells.

States of Matter

• Solid: Fixed structure.
• Liquid: Free movement within fixed volume.
• Gas: Fills any volume, high entropy.
• Plasma: Ionized gas at high temperatures.

Mixtures and Solutions

• Homogeneous Mixtures: Even distribution (e.g., salt in water).
• Heterogeneous Mixtures: Distinct regions (e.g., sand in water).
• Colloids/Emulsions: Particles evenly distributed but not dissolved (e.g., milk).

Acids and Bases

• pH Scale: Measures acidity/basicity; based on hydronium ion concentration.
• Acid-Base Reactions: Neutralization forms water and salt.

Redox Reactions

• Reduction-Oxidation (Redox): Transfer of electrons, changes oxidation numbers.
• Rules for determining oxidation states.