LIEN KET HOA HOC
3.61. Cdu tao tinh thi cfta kim loai cd ddc trung quan trgng nhd't la cac ion va
nguyen tft d cdc nut mang chi cd thi dao ddng xung quanh vi trf cdn bdng ma khdng di chuyin dugc. Cdc electron hod tri chuyin ddng tg do trong toan khdi kim loai.
Chuyin ddng daO ddng cua cdc ion vd nguyen tft tdng theo nhiet dd va thi hien nhiet dd cfta khd'i kim loai. Khi ddt ndng mdt ddu thanh kim loai, cdc ion va nguyen tft chuyin ddng tdng ddn va truyin ndng lugng cho cdc ion va nguyen tft ldn cdn (gid'ng nhu su truyin ndng lugng trong cdc chdt rdn khac). Cdc ion vd nguyen tft cdn truyin ndng lugng cho electron tg do. Cdc electron khdng chi truyin ndng lugng cho cdc ion vd nguyen tft ldn cdn ma cdn truyin ndng lugng cho cdc ion vd nguyen tft d xa ban vi thi ndng lugng dugc truyin di nhanh ban, kim loai ddn nhiet tdt.
Cdc electron trong khd'i kim loai chuyin ddng khd tu do trong tinh thi kim loai nen khi tac dung lgc dien (dien trudng) cdc electron se di chuyin dl dang trong dien trudng ma tdn rd't it ndng lugng. Kim loai ddn dien tdt. Khi chiu tac dung cfta lgc co hgc thi eac ion va nguyen tft bi di chuyin, chung bi xd lech. Cdc electron trong khd'i kim loai cd tuong tdc chat che vdi cdc ion ma lai rd't linh ddng do "khf" electron ma khoang each gifia cdc ion vd nguydn tft vdn dugc gift nguyen nhu trudc. Do dd kim loai dl ddt mdng vd keo thanh sgi (thi hien tfnh deo).
3.62. Thi tfch cfta 1 mol sdt = 55,85 g/7,87 g/cm^ = 7,097 em"* ddng thdi chiia
Thi tfch 1 nguyen tft sdt bdng
7,097 cm /mol ^ 1A_ ^ Q 372.lO'^^em^
6,02.10^3 mol-i 100
+ Ban kfnh nguyen tft sdt tfnh theo cdng thftc Tft dd ta cd ban kfnh nguyen tft sdt r = 1,28.10 ^cm.
———= 8,72.10 em .
3.63*.
Hinh 3.10 : Susap xep cac hat trong mgt dan vi mang li/di lap phUOng tam mat
Tft hinh ve ta thd'y ngay duge cac hat tiep xuc nhau d mat ben. Dudng cheo cua mat ben cd chiiu dai bdng 4 ldn ban kinh nguyen tft : b = 4r.
1 - 2 2 >y2a
Trong mdt d mang tinh the cd canh bang a. Ta cd (4r) = 2a ; r = —-— Thi tfch cfta 1 nguyen tft hinh cdu bdng 47n-^ Sd nguyen tft trong mdt d mang tinh thi = 4, ta cd ti le thi tich bi cac nguyen tft chie'm va thi tich
471 ^ V ^ ^ ' hop (a^) \ A ) hop (a^) \ A ) 3a' X 100 -'•- IA. Phdn trdm chidm chd bdng 74%. J Bai 24