# Formal structure of periodic system of elements

## TL;DR

This paper introduces a formal mathematical framework for the periodic system of elements using ordered hypergraphs, unifying its structure and enabling applications across various scientific disciplines.

## Contribution

It provides a novel formal structure for the periodic system based on order and similarity, extending its applicability beyond chemistry.

## Key findings

- Current periodic system is an instance of the formal structure.
- Defined a periodic system of polarizability for covalent bonds.
- Generalized the concept to other scientific disciplines.

## Abstract

For more than 150 years the structure of the periodic system of the chemical elements has intensively motivated research in different areas of chemistry and physics. However, there is still no unified picture of what a periodic system is. Herein, based on the relations of order and similarity, we report a formal mathematical structure for the periodic system, which corresponds to an ordered hypergraph. It is shown that the current periodic system of chemical elements is an instance of the general structure. The definition is used to devise a tailored periodic system of polarizability of single covalent bonds, where order relationships are quantified within subsets of similar bonds and among these classes. The generalised periodic system allows envisioning periodic systems in other disciplines of science and humanities.