The Periodic Table

The elements in the periodic table combine in different ways to form everything around us. In the periodic table, elements are arranged in order of increasing atomic number. This is the number of protons in the nucleus of an atom.

Each element is represented by a unique box that includes its name, atomic number, chemical symbol, and atomic mass.

Hydrogen, as it would appear in the periodic table: atomic number of 1, atomic symbol (H), and atomic mass of 1.0078.

Elements in the periodic table are organised by periods and groups.

Periods are the horizontal rows and there are seven in total. These rows represent the number of electron shells that an atom has. For example, elements in period 3 have 3 electron shells.

Groups are the vertical columns. They are usually labelled from 1 to 18, although in some versions, the main groups are labelled 1-8 with the final group being called group 0 or group 8. Groups show how many electrons an atom has in its outermost shell. For example, elements in group 2 have two electrons in their outermost shell.

  • Elements in the same group have similar chemical properties. This is because they have the same number of electrons in their outermost shell, which plays a significant role in how an element reacts.
A detailed periodic table of elements showing the organisation of all known elements. The table is categorised by colour-coded groups, including alkali metals, alkaline earth metals, transition metals, metalloids, non-metals, halogens, noble gases, lanthanoids and actinoids. Each element is represented by its atomic number, symbol, name and relative atomic mass. The table is also marked with vertical columns indicating groups 1 through 8 and horizontal rows indicating periods, from 1 to 7, and horizontal groups indicating groups, from 1 to 8.. The lanthanoids and actinoids are displayed separately at the bottom. Arrows and annotations explain the information provided for each element, such as atomic mass and chemical symbol, using Hydrogen as an example.