离子键 库仑键力 电子被交换Electrons are transferred 大的电负性差异Large difference in electronegetivities 强而没有方向性strong and non-directional::高熔点high melting point,硬 而脆hard but brittle,绝缘体insulator离子键  电子被交换Electrons are transferred  大的电负性差异Large difference in electronegetivities  强而没有方向性strong and non-directional: 高熔点high melting point, 硬 而脆hard but brittle, 绝缘体insulator