General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

JEE: General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

The document General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE is a part of the JEE Course Chemistry for JEE.
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Transition Elements:

Definition: They are often called "transition elements" because their position in the periodic table is between s-block and p-block elements.

Typically, the transition elements have an incompletely filled d-level. Since Zn group has d10 configuration and are not considered as transition elements but they are d-block elements.

General Characteristics:

(i) Metallic character: They are all metals and good conductors of heat & electricity.

(ii) Electronic configuration: (n – 1)d1– 10ns1–2

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

(iii) M.P.

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

(iv) Variation in atomic radius:

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

(v) Variable oxidation states possible:

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

Colour : (aquated)

Colour : (aquated)

Sc3+ → colourless

Ti4+ → colourless

Ti3+ → purple

V4+ → blue

V3+ → green

V2+ → violet

Cr2+ → blue

Cr3+ → green

Mn3+ violet

Mn2+ → light pink

Fe2+ → light green

Fe3+   yellow

Co2+ → pink

Ni2+ → green

Cu2+ → blue

Zn2+ → colourless

CHROMATE - DICHROMATE:

Preparation:

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

[Lime (CaO) added with Na2CO3 which keeps the mass porous so that air has access to all parts and prevents fusion.]
Then, 

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEEGeneral Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

NaCl crystallises out first and filtered off. Then K2Cr2O7 crystallised out on cooling

  • Other props & test of CrO42– & Cr2O72– : Already discussed
  • Similarities between hexavalent Cr & S–compounds.

General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEEGeneral Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEEGeneral Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE

Ques: In laboratory K2Cr2O7 is used mainly not Na2Cr2O7. Why?

Ans: Na2Cr2O7 is deliquescent enough and changes its concentration and cannot be taken as primary standard solution whereas K2Cr2O7 has no water of crystallisation and is not deliquescent.

Fig: Structure of Na2Cr2O7 Fig: Structure of Na2Cr2O7 

Ques: How to standardise Na2S2O3 solution in iodometry?

Ans: K2Cr2O7 is the primary standard ⇒ strength is known by weighing the salt in chemical balance and dissolving in measured amount of water.

Then in acidic solution, add KI

Cr2O72-  + 14 H+ + 6I- → 2Cr3+ + 3I2  + 7H2O

This I2 is liberated can be estimated with S2O32-.

The document General Properties of Transition Elements: The d & f- Block Elements Notes | Study Chemistry for JEE - JEE is a part of the JEE Course Chemistry for JEE.
All you need of JEE at this link: JEE

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