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CBSE Class 12 · Chemistry

The d-and f-Block Elements

Official NCERT chapter from Chemistry Part I–II (book code lech1). ExamMaster notes are original teaching at CBSE Class 12 depth.

This lesson follows the official chapter “The d-and f-Block Elements” in Chemistry Part I–II. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 12
  • Medium level
  • 8 concepts

1Position in the Periodic Table

Position: d-block is the middle of the long table as taught (groups 3–12 as framed); f-block sits apart as lanthanoids and actinoids. Position is a slot-map, not a colour.

Parking Na in the d-block because it is a metal is a miss.

Figure. d-block is groups 3–12, periods 4–7. f-block sits as the 4f lanthanoids and 5f actinoids under the table, not as a second d-block.

How it works

  1. Name the middle block or the f-rowThe position.
  2. Keep s-block metals outThe caution.
  3. Refuse a colour as the slotA map.

2Electronic Configurations of the d-Block Elements

d-block configs: (n−1)d and ns as taught, with Cr and Cu as named exceptions if listed. A config is the reason the slot was earned. Copy Z before you fill as if it were the next element.

A noble-gas dump as every d-config is a skip.

Figure. Cr is not 3d⁴ 4s². The observed writing is 3d⁵ 4s¹ — a half-filled 3d set. Cu is the other school exception: 3d¹⁰ 4s¹.

How it works

  1. Copy ZThe given.
  2. Fill (n−1)d and ns as taughtThe config.
  3. Keep Cr/Cu exceptions only if listedHonest extra.

3General Properties of the Transition Elements (d-Block)

Transition properties: variable oxidation states, coloured ions, catalytic looks as taught. A property-bundle, not one slogan. One Fe(II)/Fe(III) mention is enough.

Calling every d-ion colourless is a miss if the lesson said coloured.

Figure. Metallic radius falls from Sc (164 pm) to Cr (129 pm), then rises a little at Zn (137 pm) once 3d is full. The bars are those NCERT lengths, not decoration.

How it works

  1. Name variable OS, colour, or a catalyst-lookThe property.
  2. Keep one school caseThe example.
  3. Refuse a single slogan as the bundleSeveral looks.

4Some Important Compounds of Transition Elements

Important compounds: KMnO4, K2Cr2O7 as taught — oxidising looks in acid if framed. A compound-heading is a named use, not a new block. One oxidising-sentence each is enough.

A brand-bleach as “the same as KMnO4” is a miss.

Figure. KMnO₄ in acid becomes Mn²⁺. K₂Cr₂O₇ in acid becomes Cr³⁺. Both are oxidants; the product ion is the evidence, not a colour word.

How it works

  1. Name the taught compoundThe case.
  2. Attach the school job (oxidise, …)The use.
  3. Refuse a workshop-manualThis class.

5The Lanthanoids

Lanthanoids: 4f filling as taught; a slow radius-drop (lanthanoid contraction) if named. Lanthanoid is an f-row, not a d-row. One contraction-sentence is enough.

Calling them all identical with no contraction-word is a skip if taught.

Figure. Ln³⁺ radius falls from La (106 pm) to Lu (85 pm). That steady shrink is the lanthanoid contraction — one extra 4f electron does not cancel the rising nuclear charge.

How it works

  1. Name 4f fillingLanthanoids.
  2. Keep contraction as the extra if taughtThe look.
  3. Refuse a d-block dump hereAn f-row.

6The Actinoids

Actinoids: 5f filling as taught; many are radioactive as framed. Actinoid is the second f-row. One radioactivity-sentence is enough — not a dump of every isotope.

A lanthanoid labelled actinoid because both are “inner” is a miss if Z is wrong.

Figure. Th is mostly +4 (one common state). U and Pu each show four school-common states (+3 to +6). Actinoids are not a second copy of the lanthanoid +3 story.

How it works

  1. Name 5f fillingActinoids.
  2. Keep radioactive as a school look if taughtThe extra.
  3. Refuse a how-toThis class.

7Some Applications of d- and f-Block Elements

Applications: catalysts, alloys, magnets as taught — one honest use-column. Application is a use, not a brand-ad. One named use is enough.

A slogan “transition metals do everything” is a mute use.

Figure. School uses: iron as the Haber catalyst, titanium in light strong alloys, lanthanoids in permanent magnets. A use is not a colour.

How it works

  1. Name one taught useThe application.
  2. Keep it a school sentenceHonest.
  3. Refuse a brand-adA use-column.

8A definition is a test you can run

d/f-word is a test: a slot, a config, a variable OS, or an f-row. If you only say “heavy metal”, you have a heading.

A shiny-sticker is not the test.

Figure. A typical transition element has a part-filled d set in the atom or a common ion. Sc passes. Zn is d-block but 3d¹⁰, so it fails the typical-transition test.

How it works

  1. Name the block, the OS, or the f-rowThe object.
  2. Give the school sentenceThe test.
  3. Then the word has contentThe definition ran.
d-block sits
  1. In the middle of the long table as taught
  2. As alkali metals
  3. Only as gases

A slot-map.

Notes

  • Mapped to the official NCERT chapter “The d-and f-Block Elements”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • d-block: (n−1)d ns as taught
  • lanthanoids: 4f; actinoids: 5f

Recap

Hold these pegs from the official chapter “The d-and f-Block Elements”. The wording is ExamMaster’s teaching, not a textbook recap.

Position in the Periodic Table
Position: d-block is the middle of the long table as taught (groups 3–12 as framed); f-block sits apart as lanthanoids and actinoids.
Electronic Configurations of the d-Block Elements
d-block configs: (n−1)d and ns as taught, with Cr and Cu as named exceptions if listed.
General Properties of the Transition Elements (d-Block)
Transition properties: variable oxidation states, coloured ions, catalytic looks as taught.
Some Important Compounds of Transition Elements
Important compounds: KMnO4, K2Cr2O7 as taught — oxidising looks in acid if framed.
The Lanthanoids
Lanthanoids: 4f filling as taught; a slow radius-drop (lanthanoid contraction) if named.
The Actinoids
Actinoids: 5f filling as taught; many are radioactive as framed.

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