Lowest Atomisation Enthalpy 🔥 | d-Block Trick
❓ Question Among: Cr, Fe, Co, Ni Which metal has the lowest enthalpy of atomisation ? Find the number of valence electrons in that metal. 🖼 Question Image ✍️ Short Solution Enthalpy of atomisation depends on: 👉 Strength of metallic bonding 👉 Number of unpaired electrons More unpaired electrons ⇒ stronger bonding ⇒ higher enthalpy 🔷 Step 1 — Write Electronic Configurations 💯 Cr: [ A r ] 3 d 5 4 s 1 [Ar]\, 3d^5 4s^1 Fe: [ A r ] 3 d 6 4 s 2 [Ar]\, 3d^6 4s^2 Co: [ A r ] 3 d 7 4 s 2 [Ar]\, 3d^7 4s^2 Ni: [ A r ] 3 d 8 4 s 2 [Ar]\, 3d^8 4s^2 🔷 Step 2 — Count Unpaired Electrons Cr → 6 unpaired Fe → 4 unpaired Co → 3 unpaired Ni → 2 unpaired 🔷 Step 3 — Relation with Atomisation Enthalpy More unpaired electrons ⇒ stronger metallic bonding So: Cr > Fe > Co > Ni 👉 Lowest enthalpy = Ni 🔷 Step 4 — Valence Electrons in Ni For transition metals: Valence electrons = n s + ( n − 1 ) d ns + (n-1)d Ni: 3 d 8 4 s 2 3d^8 4s^2 Total valence elec...