Types of Elements: s-, p-, d- and f- Blocks
Slice the periodic table by the last electron’s subshell and four families emerge — each with its own configuration grammar, its own chemistry, and one famous definition dispute (are Zn, Cd, Hg really transition elements?). Every block, every group, drilled live.
The Four Families — Complete Theory
Block classification is the § 3.5 rule turned into geography: the subshell receiving the last electron names the block, and the block predicts the chemistry. Four families, four configuration grammars:
s-block (groups 1–2). Configuration ns¹⁻². Group 1 — the alkali metals (Li, Na, K, Rb, Cs, Fr): soft, low-melting, violently reactive, lowest ionization enthalpies in their periods. Group 2 — the alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra): harder, denser, still reactive. Together they are the table’s committed metals — they lose their outer electrons readily and form M⁺/M²⁺ ions. Hydrogen completes group 1 on paper (1s¹) but is really a category crisis: it loses an electron like group 1, needs one like group 17, and shares electrons like group 14 — NCERT parks it in group 1 with a warning label.
p-block (groups 13–18). Configuration ns² np¹⁻⁶. The only block that mixes everything: metals (Al, Ga, In, Sn, Pb…), metalloids (B, Si, Ge, As, Sb, Te — the staircase band), non-metals (C, N, P, O, S, halogens), and group 18’s noble gases (ns² np⁶ closed shells; helium the s-block squatter). Oxide chemistry flips from metallic to non-metallic as you move right — the trend engine of § 3.7 runs at full power here.
d-block (groups 3–12). Configuration (n−1)d¹⁻¹⁰ ns⁰⁻² — the transition elements. All metals, hard, high-melting, variable oxidation states, coloured ions, catalytic powers — all because that inner d subshell sits close in energy to ns and participates in bonding. But the definition is stricter than the geography: a transition element is one whose atom or at least one common ion has a partially filled d subshell. That clause evicts zinc, cadmium and mercury — d-block residents, but with d¹⁰ in the atom and in their common M²⁺ ions, they never qualify. The d-block also hosts the f-series openers (La, Ac) and, in periods 6–7, swallows the f-block’s seats.
f-block. Configuration (n−2)f¹⁻¹⁴ (n−1)d⁰⁻¹ ns² — the inner transition elements, because the differentiating electron buries itself two shells deep. The lanthanoids (4f, Ce–Lu, period 6) and actinoids (5f, Th–Lr, period 7) all belong to group 3 but are printed as two rows below the main table — otherwise the table would need 32 columns. All are metals; the actinoids are all radioactive, and the lanthanoids’ gradual size shrinkage across the series (the lanthanoid contraction) is the reason 4d and 5d rows have nearly identical radii — a detail that pays off in coordination chemistry.
| Block | General config | Groups | Character | Key members |
|---|---|---|---|---|
| s | ns¹⁻² | 1, 2 | All metals (H: exception) | Na, K, Mg, Ca |
| p | ns² np¹⁻⁶ | 13–18 | Metals + metalloids + non-metals | B, C, N, O, Al, Cl, Ne |
| d | (n−1)d¹⁻¹⁰ ns⁰⁻² | 3–12 | All metals — transition (Zn/Cd/Hg excluded) | Sc, Fe, Cu, Ag, Hg* |
| f | (n−2)f¹⁻¹⁴ ns² | 3 (rows below) | All metals — inner transition; actinoids radioactive | Ce–Lu, Th–Lr |
Metals, non-metals, metalloids — the census. Roughly 78% of the 118 elements are metals (s, d, f blocks plus the p-block’s left flank), about 20 are non-metals (H, C, N, O, P, S, Se, halogens, noble gases), and the six metalloids — B, Si, Ge, As, Sb, Te — form the staircase. Non-metals are fewer but dominate the chemistry of life; metals dominate the chemistry of industry. The staircase’s position also marks where metallic character (§ 3.7) flips sign in every period.
Visualising the Blocks & Drilling the Address
Ek naksha, ek drill — the block map first, then convert ten configurations into block-period-group triples against the clock.
Block Drill
Config dikhegi — aap block, period aur group predict karo. Teeno sahi hote hi item green; guess karne se pehle block rules revise kar lo.
[Ne] 3s² 3p⁴
Which element’s configuration is this — and where does it sit?
Drill items include the exam’s favourite traps: Cr and Cu (exception configs), Ag, Lu (f-block group 3), and At (period 7 p-block).
Solved Examples (Step-by-Step)
Config → family → verdict. Jo reasoning yahan chalti hai, wahi drill me live chalti hai.
Zinc: resident, not member
Zinc (Z = 30) has the configuration [Ar] 3d¹⁰ 4s². Is zinc a transition element? Justify using the definition.
- BlockLast electron enters 3d → d-block, group = 10 + 2 = 12.
- Definition testTransition requires a partially filled d in the atom or a common ion.
- Atom3d¹⁰ — filled. Ion: Zn²⁺ = [Ar] 3d¹⁰ — still filled.
- VerdictZn is d-block but not a transition element — Cd and Hg repeat the pattern (4d¹⁰, 5d¹⁰).
d-block yes · transition no — the definition decides
Why period 4 holds exactly 18 elements
Show, using configurations, that the fourth period contains 18 elements, and name its first and last members.
- Fill orderPeriod 4 fills
4s, 3d, 4p— capacities 2 + 10 + 6. - Sum
2 + 10 + 6 = 18 elements— from K (4s¹) to Kr (4s² 3d¹⁰ 4p⁶). - MapK, Ca (4s) → Sc…Zn (3d, ten elements) → Ga…Kr (4p, six).
- ComparePeriod 3 lacked a d-subshell → only 8 elements. The d-entry is why periods double in length.
2 + 10 + 6 = 18 · K → Kr
Uranium’s passport
Uranium (Z = 92) has configuration [Rn] 5f³ 6d¹ 7s². Identify its block, series, group and one property unique to its family.
- SeriesZ = 92 lies in 90–103 → actinoid (5f) series, period 7.
- BlockDifferentiating electron region is 5f (n−2) → f-block, an inner transition element.
- GroupAll f-block elements → group 3, displayed in the second row below the table.
- Family traitActinoids are all radioactive — U’s radioactivity is a family certificate, not an individual accident.
f-block · actinoid · group 3 · radioactive family
Practice Questions (With Solutions)
Attempt first — options lock after one shot, exactly like the real exam. Then read the working, chahe galti ho ya na ho.
Attempted 0/4 · Correct 0
Which of the following d-block elements is not considered a transition element?
Solution
- Cd carries 4d¹⁰ in the atom and in Cd²⁺ — no partially filled d anywhere → fails the transition definition.
- Sc (d¹ in atom and Sc³⁺… well, d⁰ in Sc³⁺ but d¹ in atom suffices), Fe and Cr all qualify. Zn, Cd, Hg are the standing exclusions.
(C) Cd
The lanthanoids and actinoids are placed in group:
Solution
- The entire f-block — 4f and 5f series alike — is assigned to group 3, displayed as two rows below the table.
- Placement below keeps the table at 18 columns; a 32-column monster would be unreadable.
(B) Group 3
Which of the following sets contains only metalloids?
Solution
- The six metalloids: B, Si, Ge, As, Sb, Te — the staircase through groups 13–16.
- Option A is the classic partial list (Sb and Te missing); D mixes a true metal (Al) with non-metals.
(C) All six
Hydrogen’s placement in group 1 is justified partly because it resembles groups:
Solution
- Like group 1: H⁺ by losing 1s¹. Like group 17: H⁻ by gaining one electron to close the shell. Like group 14: covalent H–H sharing.
- Triple resemblance is why H gets its own category crisis — a flat “alkali metal” claim is the trap.
(C) 1, 17 and 14
Key Takeaways & Block Card
Eight lines that solve this topic
Config grammars: s ns¹⁻² · p ns²np¹⁻⁶ · d (n−1)d¹⁻¹⁰ns⁰⁻² · f (n−2)f¹⁻¹⁴(n−1)d⁰⁻¹ns² · Series: Ce–Lu (4f), Th–Lr (5f)
- Block = grammar, family = behaviour — each block’s config pattern predicts its group range and dominant character before any data is seen.
- The definition clause evicts three residents — Zn, Cd, Hg are d-block geography but fail transition membership; quote “partially filled d in atom or common ion”.
- f-block is group 3’s underground — two 14-element rows (La/Ac open the series); all metals, actinoids radioactive.
- H belongs to three families and none — H⁺ like group 1, H⁻ like group 17, sharing like group 14; any single-family claim is bait.
FAQs
What are the s, p, d and f blocks of the periodic table?
The four blocks are named after the subshell receiving the last electron. s-block: groups 1 and 2, configuration ns¹⁻² — alkali and alkaline earth metals. p-block: groups 13 to 18, ns² np¹⁻⁶ — metals, non-metals and metalloids. d-block: groups 3 to 12, (n−1)d¹⁻¹⁰ ns⁰⁻² — the transition elements. f-block: (n−2)f¹⁻¹⁴ — the lanthanoids and actinoids, all placed in group 3 as two rows below the table.
Why are zinc, cadmium and mercury not considered transition elements?
A transition element is defined as one whose atom or commonly formed ions have a partially filled d subshell. Zinc, cadmium and mercury have completely filled d¹⁰ configurations in both their atoms and their most common +2 ions, so they never show a partially filled d subshell — despite lying in the d-block, they do not meet the definition of transition elements.
Where are the lanthanoids and actinoids placed in the periodic table?
They are placed in group 3, but displayed as two horizontal rows below the main table: the lanthanoids (4f filling, cerium to lutetium) in period 6 and the actinoids (5f filling, thorium to lawrencium) in period 7. They are called inner transition elements because the differentiating electron enters the (n−2)f subshell, two shells inside the outermost.
What are metalloids and where are they located in the periodic table?
Metalloids — boron, silicon, germanium, arsenic, antimony and tellurium — are elements whose properties lie between metals and non-metals. They form a staircase diagonal band running through the p-block, separating the metals on the lower left (about 78% of all elements) from the non-metals on the upper right.
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