How are elements ordered in the periodic table?

Elements in the periodic table are ordered by increasing atomic number, which represents the number of protons in an atom's nucleus.

The periodic table is a systematic way of organising the chemical elements. It is arranged in rows and columns to highlight periodic trends, or recurring characteristics, in the elements. The most fundamental way that elements are ordered in the periodic table is by their atomic number. The atomic number of an element is equal to the number of protons in the nucleus of its atom. As you move from left to right across a period (row) in the table, the atomic number increases.

The table is also divided into groups (columns). Elements in the same group have the same number of electrons in their outer shell, which is why they have similar chemical properties. For example, all elements in Group 1, known as the alkali metals, have one electron in their outer shell and are highly reactive.

The periodic table is further divided into blocks, named s, p, d, and f, according to 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 contains the lanthanides and actinides.

The arrangement of the periodic table allows scientists to understand the relationships between various elements, predict the properties of new elements, and make sense of the way that atoms are put together. It's a powerful tool for studying and understanding the world at the atomic level.