Electronic Configurations and Types of Elements: s-, p-, d-, f- Blocks

Full Notes

Overview

The periodic table is divided into blocks based on the subshell in which the last electron enters during the electronic configuration. This classification reflects the elements’ chemical properties, reactivity, and periodic trends.

3.6.1 The s-Block Elements

Comprise Groups 1 and 2, plus helium

• Their general configuration is ns¹ (Group 1) or ns² (Group 2)
• Helium (1s²) is also part of the s-block, though it's placed in Group 18 due to its inert nature

Characteristics:

• Highly reactive metals.
• Readily lose electrons to form +1 (Group 1) or +2 (Group 2) cations.
• Found in alkali metals and alkaline earth metals.
• Stored under oil or inert conditions due to high reactivity (especially alkali metals).
• Reactivity increases down the group.

3.6.2 The p-Block Elements

Includes Groups 13 to 18. General outer configuration: ns² np^1–6. Represents the last six groups on the right side of the periodic table.

• Characteristics:
• Diverse in properties: includes metals, non-metals, and metalloids.
• Shows all types of bonding: ionic, covalent, and coordinate.
• Reactivity patterns:
  • Non-metals dominate the top right (e.g., F, O, N).
  • Metals dominate the bottom left of the block.
• Contains important families:
  • Group 17: Halogens – highly reactive non-metals.
  • Group 18: Noble gases – inert, full octets.

3.6.3 The d-Block Elements (Transition Elements)

Occupy Groups 3 to 12. General configuration: (n–1)d^1–10 ns^1–2. Known as transition elements because they bridge s- and p-blocks.

• All are metals.
• Exhibit variable oxidation states.
• Form colored compounds.
• Often act as catalysts (e.g., Fe, Pt).
• Involve partially filled d-orbitals.
• Form complex ions such as [Fe(CN)₆]⁴⁻.

3.6.4 The f-Block Elements (Inner-Transition Elements)

Two series: Lanthanides (Z = 58–71) and Actinides (Z = 90–103). General configuration: (n–2)f^1–14 (n–1)d^0–1 ns².

• Characteristics:
• Placed below the main periodic table to maintain structure.
• All are metals, many radioactive (especially actinides).
• Exhibit variable oxidation states.
• Known for complex chemistry and similarity among elements.
• Lanthanides: Rare earth elements used in magnets and phosphors.
• Actinides: Include uranium and thorium, used in nuclear energy.

3.6.5 Metals, Non-Metals and Metalloids

Elements in the periodic table can be further classified as metals, non-metals and metalloids, based on their properties.

Elements become less metallic (metal-like) as you move across a period and more metallic as you go down a group.

Metals

• Mostly found in s-, d-, and lower p-blocks.
• Malleable, ductile, shiny, good conductors of heat and electricity.
• Generally have high melting and boiling points.
• Tend to lose electrons and form cations.

Non-Metals

• Located mostly in the upper right corner of the periodic table.
• Found mainly in the p-block.
• Poor conductors, brittle, dull appearance.
• Tend to gain electrons and form anions.

Metalloids

• Possess intermediate properties between metals and non-metals.
• Found along the “stair-step” line (e.g., B, Si, As).
• Exhibit both metallic and non-metallic behavior.
• Important in semiconductors and electronic materials.

Summary

• Periodic table divided into s, p, d, and f blocks based on electron configuration.
• s-block: reactive metals; p-block: diverse properties; d-block: transition metals; f-block: inner transition metals.
• Metals dominate the left and center; non-metals on the right; metalloids bridge them.
• Block classification explains periodic properties and chemical reactivity patterns.