- vdi phi kim manh Cdng thftc hoa hoc ciia :
Y NGHTA CUA BANG TUAN HOAN CAC NGUEN TO HOAHOC 2.30 C.
2.43. Hai kim loai cun gd nhdm IIA nen cd cung tfnh chd't hod hgc, cung th
hien hod tri 2 va cd the thay bdng mdt kim loai tuang duang M. Kim loai tuang duang M cd khdi lugng mol nguyen tft ndm trong khoang gia tri khd'i lugng mol nguyen tft cua hai nguyen td cdn tim.
Ta cd phuang trinh hod hgc :
M + 2HC1-> MCI2 + H2t
Theo phuang trinh hod hgc, sd mol hai kim loai (hay sd mol kim loai tuang duang) bdng sd mol hidro = 3,36 dm^/22,4 dm'^/mol = 0,15 mol.
4 4 p
Khd'i luang mol nguyen tft trung binh cua M la : —-—^—= 29 33 g/mol
0,15 mol ' thudc khoang khd'i lugng mol nguyen tft eua magie va canxị Vdy hai kim loai cdn tim la Mg va Cạ
Chucmg 3 . _ ^ _ _ _ ^ _ , . . ^ _
LIEN KET HOA HOC
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K H A I NIEM VE LIEN KET HOA HOC. LIEN KET ION
3.1. Cac nguyen tft khf hiem diu cd cd'u hinh electron ldp ngoai cung dac biet bin vftng : ns np (trft heli cd cau hinh Is ). Cac nguyen tft khf hiem rat khd tham gia phan ftng hod hgc. Trong tg nhien, cac khi hilm diu tdn tai d dang nguyen tft (hay cdn ggi la phan tft mdt nguyen tft) tu do (nen cdn ggi la cac khi tro).
Cac nguyen tft cua cdc nguyen td khac khdng cd cd'u hinh electron nguyen tft gidng cdc khi hiem nen cd xu hudng dat den ldp vd electron cua cae khf hidm. Cdc nguyen tft cfta cung nguyen td lien kit vdi nhau tao ra cac phdn tft dan chd't nhu H2, O2, CI2...
Cdc nguyen tft cua cdc nguyen td lien kit vdi nhau tao ra cac phdn tft hgp chd't : HCI, CO2... hay tu tap hgp lai thanh cac khdi don chdt nhu kim cuong, than chi, photpho rdn...
Trong nhiing phdn tft tao thanh tft cdc nguyen tft, cd'u hinh electron cua tiing nguyen tft thudng gid'ng cdu hinh electron nguyen tft cua khf trạ Do đ, phdn tft hay tinh thi cd ndng lugng thdp ban tdng nang lugng cua tiing nguyen tft rieng rẹ Nhu vdy, nguyen nhdn dl tao thanh lien kit hoa hgc va tao thanh
phdn tft la khuynh hudng liin kít cdc nguyin tic cua cdc nguyen td hod hgc
dedqt tdi cdu hinh electron nguyen tdcua khi hiím.
3.2. a) Nguyen tft kali chi cd 1 electron d ldp vd ngoai cung nen dl dang nhudng di electron nay de tao thanh ion K"^. Ion K"^ cd cd'u hinh electron cua khi hidm agon dftng trudc kalị
Nguyen tft brom thi ngugc lai cd 7 electron d ldp ngoai cung nen dl dang nhdn them 1 electron tao ra ion Br~ cd cd'u hinh electron cua khi hiem kripton.
b) Cdc ion K"^ va ion Br" hut nhau bdng luc hut tinh dien de tao ra lien kit ion. Phdn tft kali bromua cd ndng lugng thdp ban tdng ndng lugng cua nguyen tft kali va brom rieng rẹ
2 5
3.3. Nguyen tft flo cd cd'u hinh electron ldp ngoai cung la 2s 2p . Khi nhdn them 1 electron, nguyen tft flo bidn thanh ion florua vdi cd'u hinh electron
9 9 6
đy du la Is 2s 2p cfta khi hidm neon. Ion florua cd 8 electron d ldp ngoai cung (thoa man quy tdc bat tft).
Nguyen tft kali thi ngugc lai, cd 1 electron d ldp electron ngoai cung nen de dang cho di 1 electron tao ra cation kali (K"^) cd cd'u hinh electron cua khf hidm agon.
Nhu vdy, lieh kit cua cac anion florua va cation kali dugc thgc hidn bdng luc hut tinh didn va thudc loai lien kdt ion.
2
3.4. Nguyen tft canxi cd cd'u hinh electron ldp ngodi cung la 4s . Khi cho di 2 electron, nguyen tft canxi bién thanh cation Ca "^ vdi cd'u hinh electron
9 9 A 9 6 9-+-
đy du la Is 2s 2p 3s 3p cua khi hidm agon. Cation Ca cd 8 electron d ldp ngoai cung (thoa man quy tdc bat tft).
Nguyen tft flo dl nhdn them 1 electron de bidn thanh anion florua vdi cd'u hinh electron cua khi hidm neon. Ion florua cd 8 electron d ldp ngoai cung (thoa man quy tdc bat tft).
Nhu vdy, lien kit cua cdc ion Ca "^ vd F dugc thuc hien bdng luc hut tmh dien va thudc vl lien kit ion. Phdn tft canxi florua cd thi bilu diln bang cdng thftc CaF2.
, 9 9 A
3.5. Cd'u hinh electron cfta cation R la Is 2s 2p do mat 1 electron d phdn ldp ke tilp. Phdn ldp ke tidp vdi phdn ldp 2p la phdn ldp 3s. Cd'u hinh
9 9 A 1
electron cfta nguyen tft R la Is 2s 2p 3s . Nhu vdy, nguyen tft R cd 11 electron, R la nguyen tft natrị Ban chd't cfta lien kdt giua natri vd flo la lien ket ion. Trong phdn tft natri florua, ion natri cd dien tfch bdng 1+ va ion florua cd dien tfch bdng 1-.
3.6. Khi nhdn electron, nguyen tft X bidn thanh anion X . Nhu vdy, nguyen tft
9 9 f\ 0 ^
X cd cdu hinh electron la Is 2s 2p 3s 3p vdi 17 electron. Dd la nguyen td clo, mdt phi kim diln hinh.
Bari la kim loai diln hinh d chu ki 6, nhdm IIẠ Bari dl nhudng 2 electron ngoai cung vd tao ra cation cd dien tfch 2+. Khi clo kd't hgp vdi bari, su cho - nhdn electron xay rạ Nguyen tft bari nhudng 2 electron cho hai nguyen tft clo (mdi nguyen tft clo nhdn 1 electron). Cdc ion trdi đu hut nhau tao thanh lien kdt ion tao ra phdn tft bari clorua trung hod dien. Trong trudng hgp nay cation bari cd dien tfch bdng 2+, anion clorua cd dien tfch bdng 1-. Phdn tft mudi bari clorua trung hoa didn cd cdng thftc phdn tft la BaCl2.
Na O liJ iUJ 1 2 T 2 Is 2s HUH] 2P^ I I 1 1 m 3s 1 z ^ z Is 2s 2p^
Khi cho natri tdc dung vdi oxi, nguyen tft natri nhudng di electron hod tri duy nhd't dl tao thanh ion Na"^ cd 8 electron gid'ng nhu nguyen tft khi hilm neon. Nguyen tft oxi cd 6 electron d ldp ngoai cung nhan them 2 electron tft hai nguyen tft natri tao thanh ion O cd 8 electron gid'ng nhu khf hilm neon. Cac ion natri va oxi diu dugc thoa man quy tdc bat tft trong phan tft natri oxit. Cd thi bieu diln cdng thftc cua hgp chd't tao thanh la Na - O - Nạ
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LIEN KET CONG HOA TR!
3.9. Lien kit cdng hod tri la lien kit dugc tao ra do su dung chung mdt hay nhilu cap electron cua cac nguyen tft trong phdn tft. _
Phdn tft H2 CO 1 lien kit cdng hod tri va dugc bieu diln bdng cdng thftc cdu tao la : H - H
Phdn tft clo cd mdt lien kit cdng hod tri va dugc bilu diln bang cdng thftc cd'u tao la : Cl - Cl
Phdn tft hidro clorua cd 1 lien kit cdng hod tri : H - Cl Phdn tft nita cd 3 lien kit cdng hoa tri : N = N