The Solid State
Face-centred cube dekh ke 14 spheres gin-na sabse common galti hai — corner atom 8 cells se share hota hai, face atom 2 se. Is lab mein har sphere ko uske exact hisse tak kaat sakte ho: corner ⅛ ban jaata hai, face ½, aur leftovers live reassemble hoke Z poore atoms dikhate hain. Orange diagonal batata hai atoms KAHAN touch karte hain — wahi a–r relation deta hai: edge pe a=2r, body diagonal pe √3a=4r, face diagonal pe √2a=4r. Voids toggle se tetrahedral/octahedral holes dikh-te hain, aur density panel mein ρ = ZM/a³N_A ka poora worked example chalta hai. Z, packing efficiency, a–r relation, voids, density — poore chapter ke numericals isi ek scene se nikalte hain.
Lattice badlo, orange diagonal follow karo — wahi a–r relation hai. Fractional share ON karke dekho corner atom ka sirf ⅛ hissa is cell ka hai.
Sodium metal crystallises in a body-centred cubic lattice with edge length a = 4.29 Å. If the atomic mass of Na is 23 g/mol and N_A = 6.022 × 10²³ mol⁻¹, the density of sodium is approximately:
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