How are elements arranged in the periodic table?

Elements in the periodic table are arranged in order of increasing atomic number, grouped by similar chemical properties.

The periodic table is a systematic way of organising the chemical elements, which are the building blocks of matter. It is arranged in rows and columns, with each box representing a different element. The elements are ordered by their atomic number, which is the number of protons in an atom's nucleus. This means that as you move from left to right across a row (also known as a period), the atomic number increases.

The table is also divided into groups, which are the vertical columns. Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell. This outer shell, also known as the valence shell, is crucial in determining an element's reactivity and bonding behaviour. For example, all elements in Group 1, known as the alkali metals, are highly reactive because they have one electron in their outer shell.

The periodic table is further divided into blocks, named s, p, d, and f, based on the subshell that is being filled with electrons. The s-block includes Groups 1 and 2, the p-block includes Groups 13 to 18, the d-block contains the transition metals, and the f-block includes the lanthanides and actinides.

The arrangement of the periodic table allows scientists to understand patterns and trends among the elements. For instance, elements in the same group tend to behave similarly, while elements in the same period show trends in atomic radius, ionisation energy, and electronegativity. This makes the periodic table an invaluable tool in the study and application of chemistry.