s, p, d and f Block Elements — Revision Notes

⚡ 30-Second Revision

s-block: — Groups 1 & 2. $ns^{1-2}$. Highly reactive metals, low IE, strong reducing agents, form ionic compounds, characteristic flame colors. \n- p-block: Groups 13-18. $ns^2np^{1-6}$. Metals, non-metals, metalloids. Variable oxidation states, inert pair effect (heavier elements), acidic/basic/amphoteric oxides. \n- d-block: Groups 3-12 (Transition metals). $(n-1)d^{1-10}ns^{1-2}$. Hard, dense metals. Variable oxidation states, colored ions, catalytic, complex formation, paramagnetic. Exceptions: Cr ($3d^54s^1$), Cu ($3d^{10}4s^1$). \n- f-block: Lanthanides & Actinides (Inner transition metals). $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$. Heavy metals. Lanthanoid/actinoid contraction. Lanthanides: mainly +3. Actinides: radioactive, wider oxidation states.

2-Minute Revision

The periodic table is divided into s, p, d, and f blocks based on the orbital where the differentiating electron resides. S-block elements (Groups 1 & 2) are highly reactive metals with low ionization enthalpies, forming stable +1 or +2 ions and exhibiting characteristic flame colors.

P-block elements (Groups 13-18) are diverse, including metals, non-metals, and metalloids, showing variable oxidation states, with the inert pair effect becoming significant for heavier elements. D-block elements (transition metals) are characterized by variable oxidation states, formation of colored compounds, catalytic activity, and complex formation, due to the participation of both $ns$ and $(n-1)d$ electrons in bonding.

F-block elements (inner transition metals - lanthanides and actinides) are known for the lanthanoid/actinoid contraction, which significantly impacts the radii of subsequent d-block elements. Lanthanides primarily show a +3 oxidation state, while actinides are largely radioactive and exhibit a wider range of oxidation states.

Key concepts for NEET include periodic trends, electronic configuration exceptions, and the specific properties of each block.

5-Minute Revision

A comprehensive understanding of s, p, d, and f block elements is crucial for NEET. The classification hinges on the differentiating electron's orbital. \n\ns-Block (Groups 1 & 2): These are highly electropositive metals with general configuration $ns^{1-2}$.

They have low ionization enthalpies, readily lose electrons to form $M^+$ or $M^{2+}$ ions, and are strong reducing agents. Their compounds are typically ionic and colorless. A key property is their characteristic flame coloration (e.

g., Na-golden yellow, K-lilac) due to electron excitation. Reactivity increases down the group. \n\np-Block (Groups 13-18): With general configuration $ns^2np^{1-6}$, this block is a melting pot of metals, non-metals, and metalloids.

Metallic character increases down a group, while non-metallic character increases across a period. They exhibit variable oxidation states, with the 'inert pair effect' (reluctance of $ns^2$ electrons to bond) becoming prominent for heavier elements (e.

g., +2 for Pb being more stable than +4). Their oxides can be acidic, basic, or amphoteric. Halogens (Group 17) are strong oxidizing agents, and noble gases (Group 18) are largely inert. \n\nd-Block (Groups 3-12, Transition Elements): These metals have a general configuration of $(n-1)d^{1-10}ns^{1-2}$.

Their defining features include variable oxidation states (due to small energy difference between $(n-1)d$ and $ns$ orbitals), formation of colored ions (d-d transitions), catalytic activity, and the ability to form complex compounds.

Most are paramagnetic due to unpaired d-electrons. Key exceptions in electronic configuration are Cr ($[Ar]3d^54s^1$) and Cu ($[Ar]3d^{10}4s^1$) due to orbital stability. \n\nf-Block (Lanthanides & Actinides, Inner Transition Elements): With configuration $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$, these elements are placed separately.

The most significant phenomenon is 'lanthanoid contraction' (for 4f series) and 'actinoid contraction' (for 5f series), a steady decrease in atomic/ionic radii due to poor shielding by f-electrons. This contraction leads to similar radii and properties for 4d and 5d elements in the same group (e.

g., Zr and Hf). Lanthanides primarily show a +3 oxidation state, while actinides are mostly radioactive and exhibit a wider range of oxidation states. \n\nExample: Why is $Fe^{2+}$ colored but $Zn^{2+}$ colorless?

\nSolution: $Fe^{2+}$ has electronic configuration $[Ar]3d^6$. It has four unpaired d-electrons. These unpaired electrons can undergo d-d transitions by absorbing visible light, making $Fe^{2+}$ ions colored.

$Zn^{2+}$ has electronic configuration $[Ar]3d^{10}$. All its d-orbitals are completely filled, meaning there are no unpaired d-electrons and no possibility of d-d transitions. Hence, $Zn^{2+}$ ions are colorless.

Prelims Revision Notes

1
Block Definition: — Based on the orbital of the differentiating electron (last electron). \n * s-block: $ns^{1-2}$ \n * p-block: $ns^2np^{1-6}$ \n * d-block: $(n-1)d^{1-10}ns^{1-2}$ \n * f-block: $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$ \n2. s-Block Elements (Groups 1 & 2): \n * Properties: Highly reactive metals, low ionization enthalpy (IE), strong reducing agents. \n * Oxidation States: Group 1 (+1), Group 2 (+2). \n * Compounds: Predominantly ionic, colorless. \n * Flame Test: Characteristic colors (Li-crimson, Na-golden yellow, K-lilac). \n * Trends: Reactivity and metallic character increase down the group. IE decreases down the group. \n3. p-Block Elements (Groups 13-18): \n * Diversity: Contains metals, non-metals, metalloids. \n * Inert Pair Effect: Prominent in heavier elements (e.g., Tl, Pb, Bi), leading to stable oxidation states two units less than the group number (e.g., +1 for Tl, +2 for Pb). \n * Oxides: Can be acidic (non-metals), basic (metals), or amphoteric (metalloids/some metals). \n * Halogens (Group 17): Highly reactive non-metals, strong oxidizing agents. \n * Noble Gases (Group 18): Stable, generally unreactive due to complete octet. \n4. d-Block Elements (Groups 3-12, Transition Elements): \n * Physical: Hard, high melting/boiling points, good conductors. \n * Electronic Configuration Exceptions: Cr ($3d^54s^1$), Cu ($3d^{10}4s^1$) due to half-filled/fully-filled stability. \n * Chemical: Variable oxidation states (small energy difference between $ns$ and $(n-1)d$ orbitals). \n * Colored Ions: Due to d-d transitions (unpaired d-electrons). \n * Catalytic Activity: Many act as catalysts (e.g., Fe, Ni, V$_2$O$_5$). \n * Complex Formation: Due to small size, high charge, and vacant d-orbitals. \n * Magnetic Properties: Paramagnetic (unpaired electrons), Diamagnetic (all paired electrons). \n5. f-Block Elements (Lanthanides & Actinides): \n * Lanthanides (4f series): Ce to Lu. Mostly +3 oxidation state. \n * Actinides (5f series): Th to Lr. Mostly radioactive, wider range of oxidation states. \n * Lanthanoid Contraction: Steady decrease in atomic/ionic radii across the series due to poor shielding of 4f electrons. \n * Consequences of Contraction: Similar radii and properties of 4d and 5d elements in the same group (e.g., Zr and Hf).

Vyyuha Quick Recall

S-P-D-F: Simple People Don't Forget (the last electron's home).