What Are the 118 Elements and How Are They Organized in the Periodic Table?

The 118 elements are all the known chemical elements, ordered by atomic number — the number of protons in an atom's nucleus. Each element has a unique atomic number from 1 (hydrogen) to 118 (oganesson), and the periodic table arranges them in rows and columns so that elements with similar behavior line up together. You can read an element's identity and key data from its table entry, and use the table's structure to predict properties and trends.

How the periodic table is organized

The table is built on two organizing rules:

• Increasing atomic number — elements run left to right, top to bottom, from 1 to 118.
• Repeating (periodic) properties — because electron configurations repeat in patterns, elements in the same column behave similarly.

Periods (rows)

A period is a horizontal row. There are 7 periods. Moving across a period, atomic number increases by one each step, and properties shift gradually — for example, from reactive metals on the left toward nonmetals and noble gases on the right.

Groups (columns)

A group is a vertical column. Elements in the same group share the same number of valence (outer) electrons, which is why they react in similar ways. Notable groups include:

The main categories of elements

Across the table, elements fall into three broad classes:

• Metals — the majority, occupying the left and center. They tend to be shiny, conductive, and malleable.
• Nonmetals — upper-right region plus hydrogen. They tend to be poor conductors and include gases like oxygen and nitrogen.
• Metalloids — a narrow band between metals and nonmetals (e.g., silicon, germanium) with mixed properties.

How to read an element entry

A standard element tile gives you several pieces of information at once. Using an interactive table such as Zperiod, you can select an element and view its data directly. A typical entry includes:

• Symbol — the one- or two-letter abbreviation (e.g., Na for sodium).
• Atomic number — the number of protons, which defines the element.
• Atomic mass — the average mass of its atoms, in atomic mass units.
• Common properties — such as density or melting point, often with unit options. Zperiod, for example, lists units for temperature (°C, °F, K), density (g/cm³, kg/m³, lb/ft³), and energy (kJ/mol, eV).

Reading these fields together lets you compare elements and see trends — for instance, density generally increases down a group.

Synthetic elements and what the table predicts

Elements up to uranium (atomic number 92) occur naturally in meaningful amounts. Elements beyond uranium are mostly synthetic — created in laboratories and often existing only briefly before decaying. Oganesson (118) sits at the current end of the table.

The table's real power is prediction: because position reflects electron structure, you can infer an element's likely reactivity, the ions it forms, and how it compares to its neighbors — even for elements that are rare or short-lived.

If you want to explore these 118 elements interactively — rotating 3D atom models, checking ions, and comparing data — Zperiod provides a full periodic table workspace. Note that its full experience is described as desktop-oriented, with a prompt to open it on a computer for the complete workspace.