Why do we have different blocks on the periodic table?

The periodic table is organized into different blocks based on the electron configurations of the elements, specifically which atomic orbitals are being filled with electrons. The periodic table can be divided into four blocks: s-block, p-block, d-block, and f-block.

1. s-block: This block includes the first two groups of the periodic table: Group 1 (alkali metals) and Group 2 (alkaline earth metals), as well as hydrogen and helium. The s-block elements have their last electrons entering the s orbital. The s orbital can hold a maximum of two electrons, so the s-block is two groups wide.

2. p-block: This block is on the right side of the periodic table and encompasses Groups 13 to 18. The p-block elements have their last electrons entering the p orbitals, which can hold a maximum of six electrons. Since there are three p orbitals (p_x, p_y, p_z), the p-block is six groups wide.

3. d-block: Also known as the transition metals, the d-block elements are found in Groups 3 to 12. Their last electrons are filling the five d orbitals, which can hold up to ten electrons. Therefore, the d-block spans ten groups across the table.

4. f-block: This block contains the lanthanides and actinides, which are placed separately at the bottom of the periodic table to maintain its compact form. The f-block elements have electrons filling the f orbitals, which can hold up to fourteen electrons as there are seven f orbitals.

These blocks are helpful because they indicate the type of element, its properties, and its reactivity. For instance, elements in the s-block are typically metals with high reactivity, while d-block elements are metals with variable oxidation states and form different types of compounds.