Why is the periodic table divided into blocks?

The periodic table is divided into blocks to categorise elements based on their electron configuration.

The periodic table is a systematic way of organising the chemical elements, and its division into blocks is a reflection of the electron configuration of the atoms of these elements. The electron configuration refers to the distribution of electrons in an atom's electron shells. This configuration plays a crucial role in determining the chemical behaviour of an element, hence the need to categorise elements with similar configurations together.

The periodic table is divided into four blocks: the s-block, p-block, d-block, and f-block. The s-block consists of groups 1 and 2, including hydrogen and helium. These elements have their outermost electrons in the s orbital. The p-block comprises groups 13 to 18, with their outermost electrons in the p orbital. The d-block, also known as transition metals, spans groups 3 to 12, and their defining characteristic is having their penultimate energy level's d orbital filled with electrons. Lastly, the f-block, or inner transition metals, includes the lanthanides and actinides, which have their two innermost f orbitals filled with electrons.

Each block's name corresponds to the type of orbital that is being filled with electrons in the atom's ground state. This division helps in predicting the properties of the elements, their reactivity, and their possible chemical reactions. For instance, elements in the same block often share similar properties and exhibit a clear trend in properties across the block. This makes the periodic table a powerful tool in the study of chemistry, as it allows for the prediction of element behaviour and the identification of trends.