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Therefore, ions do not usually exist on their own, but will bind with ions of opposite charge to form a crystal lattice. The resulting compound is called an ionic compound, and is said to be held together by ionic bonding. In ionic compounds there arise characteristic distances between ion neighbours from which the spatial extension and the ...
The charge of the resulting ions is a major factor in the strength of ionic bonding, e.g. a salt C + A − is held together by electrostatic forces roughly four times weaker than C 2+ A 2− according to Coulomb's law, where C and A represent a generic cation and anion respectively. The sizes of the ions and the particular packing of the ...
The circumstances under which a compound will have ionic or covalent character can typically be understood using Fajans' rules, which use only charges and the sizes of each ion. According to these rules, compounds with the most ionic character will have large positive ions with a low charge, bonded to a small negative ion with a high charge. [25]
The lattice energy of an ionic compound depends strongly upon the charges of the ions that comprise the solid, which must attract or repel one another via Coulomb's Law. More subtly, the relative and absolute sizes of the ions influence Δ H l a t t i c e {\displaystyle \Delta H_{lattice}} .
That positive charge then exerts an attractive force on the electron cloud of the other ion, which has accepted the electrons from the aluminum (or other) positive ion. Two contrasting examples can illustrate the variation in effects. In the case of aluminum iodide an ionic bond with much covalent character is present.
There is no precise value that distinguishes ionic from covalent bonding, but an electronegativity difference of over 1.7 is likely to be ionic while a difference of less than 1.7 is likely to be covalent. [21] Ionic bonding leads to separate positive and negative ions. Ionic charges are commonly between −3e to +3e.
By definition, an acid is an ion or molecule that can donate a proton, and when introduced to a solution it will react with water molecules (H 2 O) to form a hydronium ion (H 3 O +), a conjugate acid of water. [4] For simplistic reasoning, the hydrogen ion (H +) is often used to abbreviate the hydronium ion.
A simple example of a polyatomic ion is the hydroxide ion, which consists of one oxygen atom and one hydrogen atom, jointly carrying a net charge of −1; its chemical formula is O H −. In contrast, an ammonium ion consists of one nitrogen atom and four hydrogen atoms, with a charge of +1; its chemical formula is N H + 4.