3.10
离子键
An ionic bond is a non-covalent attraction that holds two oppositely charged ions together, such as the sodium cation and chloride anion in sodium chloride.
In this case, sodium transfers its single valence electron to chlorine. This electron transfer completes the octet of electrons in each combining atom, making them more stable.
The strength of an ionic bond depends on the environment of the ionic compound.
In the air, the ions remain closely packed in a solid crystal. Because there are no polar molecules to pull the ions apart, the strong attraction between opposite charges keeps the compound stable.
But in water, polar water molecules surround the ions and weaken their attraction. The partial negative charge on oxygen is attracted to sodium ions, while the partial positive charges on hydrogen are attracted to chloride ions. This pulls ions away from the crystal, causing the compound to break apart into its ions.
当原子获得或失去电子并达到更稳定的电子构型时，它们就会形成离子。离子键是带相反电荷的离子之间的静电吸引。离子化合物在固态时是刚性和脆性的，并可在水中分解成其组成离子。相反，共价化合物则保持完整，除非化学反应破坏它们。
反电荷使离子化合物中的离子结合在一起
离子键是具有相反电荷的离子之间可逆的静电相互作用。最具反应性的元素（即，更容易发生化学反应）包括那些只有一个价电子的元素（如钾）和那些需要更多价电子的元素（如氯）。
失去电子的离子带有正电荷，称为阳离子。获得电子的离子带有负电荷，称为阴离子。阳离子和阴离子按比例结合，形成的化合物的净电荷为0。例如，化合物氯化钾 (KCl) 对每个钾离子包含一个氯离子，因为钾的电荷为+1，而氯的电荷为-1。复合氯化镁(MgCl2) 包含两个氯离子，每个氯离子对应一个镁离子，因为镁的电荷为+2。
离子在水中可以相互分离
当离子化合物以固体形式存在时，使其结合在一起的静电力很强。由于离子化合物的熔点往往很高，它们通常作为固体存在于地球表面。然而，离子键不如共价键强，因为离子可以在像水这样的化学反应液体中被拉开或溶解。溶解在水中的离子被称为化学反应，许多离子在这种形式下能够传导电流。
电解质对生物系统很重要
电解质是溶解在水中时能导电的离子。在生物系统中，电解质是渗透调节的关键，渗透调节是水在细胞膜上的平衡。电解质也有助于关键的生物过程，依赖于细胞膜上的电荷，如肌肉收缩和神经冲动。常见的生物电解质包括钙离子 (Ca2+)、钠离子(Na+)、镁离子 (Mg2+)、钾离子 (K+)、磷酸盐离子 (PO43-) 和氯离子 (Cl-)。
电解质失衡会导致严重的身体症状，甚至死亡。最常见的电解质失衡是低钠血症，血液中钠含量不足。低钠血症可能是另一种疾病的症状，也可能是由于摄入过多的水而没有充分补充钠引起的。治疗这种严重疾病的目的是恢复体内钠的平衡，使大脑、心脏和其它器官能够正常运作。
An ionic bond is a non-covalent attraction that holds two oppositely charged ions together, such as the sodium cation and chloride anion in sodium chloride.
In this case, sodium transfers its single valence electron to chlorine. This electron transfer completes the octet of electrons in each combining atom, making them more stable.
The strength of an ionic bond depends on the environment of the ionic compound.
In the air, the ions remain closely packed in a solid crystal. Because there are no polar molecules to pull the ions apart, the strong attraction between opposite charges keeps the compound stable.
But in water, polar water molecules surround the ions and weaken their attraction. The partial negative charge on oxygen is attracted to sodium ions, while the partial positive charges on hydrogen are attracted to chloride ions. This pulls ions away from the crystal, causing the compound to break apart into its ions.
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