Скачать или смотреть Chromium||Discovery|Physical Properties|Important Ore|Oxidation state|Electronic Congratulation

Chromium||Discovery|Physical Properties|Important Ore|Oxidation state|Electronic Congratulation

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Chromium (Cr)

1) Discovery

Louis Nicolas Vauquelin discovered chromium in 1797.

He discovered it from the mineral crocoite (PbCrO₄).

The name chromium comes from the Greek word “chroma” meaning color, because chromium compounds show many beautiful colors.

2) Physical Properties

Atomic Number: 24

Atomic Mass: 52

Group: 6 (Transition metal)

Period: 4

Color: Shiny, hard, silvery-gray metal

Melting Point: 1907°C

Boiling Point: 2671°C

Density: 7.19 g/cm³

Very hard and corrosion-resistant

Used in stainless steel and electroplating

3) Important Ore

The most important ore of chromium is:

Chromite (FeCr₂O₄)

Other ores:

Crocoite (PbCrO₄)

Chromite is mainly found in countries like South Africa, Kazakhstan, and India.

4) Oxidation States

Chromium shows variable oxidation states because it is a transition element.

Common oxidation states:

+2 (Chromous compounds)

+3 (Most stable and common)

+6 (Chromates and dichromates)

Examples:

CrCl₂ → +2

CrCl₃ → +3

K₂Cr₂O₇ → +6

5) Electronic Configuration

Chromium has an exceptional electronic configuration.

Expected:

[Ar] 3d⁴ 4s²

Actual (Correct):

[Ar] 3d⁵ 4s¹

Reason:
Half-filled 3d⁵ subshell is more stable. That is why one electron shifts from 4s to 3d.

If you want, I can also provide:
✔ Chemical properties
✔ Uses of chromium
✔ Short exam questions
✔ Long detailed notes for 2nd year / FSc level

Just tell me 😊