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Aula 5 Ligacoes quimicas 2pp

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Os átomos de carbono na grafita também são unidos fortemente através 
de ligações covalentes, mas só dentro de um plano, diferentemente da 
rede 3D das ligações do diamante. Estes planos de átomos de carbono 
simplesmente empilham-se uns sobre os outros, sendo as forças de 
união entre os planos, muito fracas. Os planos de átomos de carbono 
podem então deslizar facilmente uns sobre os outros, e por isto a grafita 
é importante lubrificante! 
GRAFITADIAMANTE
Ligação fraca
Ligação forte 
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³Os átomos tendem a ganhar ou perder
elétrons até que possuam uma camada
externa que contenha um dubleto (H, He e
Be) ou octeto de elétrons”
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A eletronegatividade dos átomos é o que 
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átomo de Na pode fornecer apenas um. Então
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Quanto mais profundo o 
poço de potencial maior a 
temperatura de fusão do 
material
Devido as forcas de 
repulsão aumentarem 
muito mais com a 
aproximação dos átomos 
a curva não é simétrica. 
Por isso, a maioria dos 
materiais tendem a se 
expandir quando 
aquecidos
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CARACTERÍSTICAS DOS ÍONS QUE AFETAM A 
ESTRUTURA CRISTALINA
„ CARGA
„ TAMANHO (RAIO IÔNICO)
42
CONSIDERAÇÕES SOBRE CARGA
„ Como o cristal deve ser eletronicamente neutro 
todas as cargas positivas devem ser 
contrabalançadas com um número igual de 
cargas negativas
Ex: CaF2 A relação deve ser de um átomo 
de Ca para dois de F pois:
„ Carga do Ca: +2
„ Carga do F= -1
43
Caráter Iônico e Covalente
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Polaridade da Ligação Covalente
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Ligação Covalente
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Eletronegatividade
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Ligação Covalente
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Ligação Iônica x Ligação Covalente
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