The periodic table is a tabular display of all 118 known chemical elements, ordered by increasing atomic number (number of protons) from hydrogen to oganesson. Elements are arranged in 7 horizontal rows (periods) and 18 vertical columns (groups) based on recurring atomic structure and similar chemical properties.

Key Components and Organization
Groups (Columns): Elements in the same group have similar chemical properties and the same number of valence electrons.
Periods (Rows): Indicate the number of electron shells in the atom.
Blocks: The table is divided into and
-blocks, corresponding to the filling of electron orbitals.
Metals, Nonmetals, and Metalloids: Metals are on the left, nonmetals on the top right, and metalloids lie along a stair-step line dividing them.
Lanthanides/Actinides: The two rows at the bottom are the
-block elements.

Key Trends
Atomic Radius: Increases down a group, decreases across a period.
Metallic Character: Increases going down a group and right-to-left across a period.
Electronegativity: Generally increases from left to right and bottom to top