Question 6 (c) - Chemistry CBSE Class 12 Sample Paper for 2022 Boards [Term 2] - Solutions to CBSE Sample Paper - Chemistry Class 12

Account for the following: 

(C) Zinc is a comparatively a soft metal, iron and chromium are typically hard

Answer

Metallic bonds are formed when charged ions share electrons and form a closely packed structure.

Weak metallic bonds result in softer metals like zinc, while stronger metallic bonds result in harder metals like chromium.

Cr (3d54s1) has five unpaired electrons in its d-orbitals .

• This allows it to use these electrons in metallic bonding, thus making stronger bonds.

Zn (3d104s2) has no unpaired electrons in its d-orbitals. 

• Since the electrons are already paired, they are unable to participate in bonding.
• Hence, Zinc makes weaker bonds.

As a result of these weak metallic bonds in Zn and strong metallic bonds in Cr , Zn is soft whereas Cr is hard .