The periodic table is divided into blocks based on the type of subshell in which the last electron enters. These blocks, s, p, d, and f, define the electronic configuration and chemical behaviour of elements.
Groups 1–2: The s‑Block Elements
Elements in Groups 1 and 2 are called s‑block elements because their electronic configuration ends in the s subshell.
- The s subshell can hold 2 electrons.
- These elements include highly reactive metals such as alkali and alkaline earth metals.
Subshell Capacities:
- s subshell: 2 electrons
- p subshell: 6 electrons
- d subshell: 10 electrons
- f subshell: 14 electrons
Energy Levels:
1s, 2s, 3s, 4s, 5s, 6s, 7s
2p, 3p, 4p, 5p, 6p, 7p
3d, 4d, 5d, 6d, 7d
4f, 5f, 6f, 7f
Groups 3–8: The p‑Block Elements
Elements in Groups 3 to 8 are known as p‑block elements because their electronic configuration ends in the p subshell. These include non‑metals, metalloids, and some metals, showing diverse chemical properties.
Transition Metals: The d‑Block Elements
Transition metals occupy the central part of the periodic table and are referred to as d‑block elements. Their electronic configuration ends in the d subshell. They exhibit variable valency, form colored compounds, and act as catalysts in many reactions.
Lanthanides and Actinides: The f‑Block Elements
These are also transition metals but are classified as inner transition elements. Their electronic configuration ends in the f subshell.
- Lanthanides (atomic numbers 57–71) and Actinides (atomic numbers 89–103) are part of the f‑block.
- They are known for their magnetic properties and use in advanced materials and technology.
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