The periodic table is organized as follows:

1. Rows (periods): Elements with the same number of electron shells
2. Columns (groups): Elements with similar chemical properties
3. Metals: Left side and center of the table
4. Non-metals: Right side of the table
5. Metalloids: Along the stair-step line between metals and non-metals
6. Atomic number: Increases from left to right and top to bottom
7. Element symbols: Unique one or two-letter abbreviations for each element

Main groups in the periodic table:

1. Group 1 (Alkali metals): Highly reactive, soft metals with one valence electron
2. Group 2 (Alkaline earth metals): Reactive metals with two valence electrons
3. Group 17 (Halogens): Highly reactive non-metals, often form salts with metals
4. Group 18 (Noble gases): Inert gases with full outer electron shells
5. Transition metals: Elements in the middle of the table with varying properties
6. Lanthanides and Actinides: Two rows of elements often shown separately below the main table

Electron configurations and the periodic table:

1. Aufbau principle: Electrons fill orbitals from lowest to highest energy
2. Pauli exclusion principle: No two electrons in an atom can have the same set of quantum numbers
3. Hund's rule: Electrons in the same subshell occupy orbitals singly before pairing
4. Period number: Corresponds to the highest occupied electron shell
5. Group number: Often relates to the number of valence electrons
6. Blocks: s, p, d, and f blocks correspond to the subshell being filled