Ionic bonds are formed when one participant loses electron/s (and becomes a positively charged ion known as cation) and another gains it (or them, and becomes negatively charged ion called as anion). For example, in sodium chloride, sodium loses an electron and chlorine gains it and we get an ionic compound.
The complete transfer of electrons between atoms results in very strong interactions and it takes a great deal of energy to break such bonds. This means that ionic compounds have very high melting and boiling points. For example, sodium chloride has a melting point of 801 degree Celsius and a boiling point of 1413 degree Celsius. Similarly, when dissolved in water, the ions dissociate and are capable of conducting electricity (note that as a solid, ionic compounds will not conduct electricity). Ionic compounds form crystals due to strong interactions between participating ions and hence are also brittle, not malleable, when pressure is applied.
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Ionic bond consist of a positively charged cation or metal (Na) that is attracted by electrostatic forces bounded to a negatively charged anion (Cl). These charges are a result of a loss of electron from Sodium to a Chloride atom.
Ionic bonds form an orderly arrangement known as face-centered cubic consisting of Na and Cl atoms. This pattern and electrostatic forces are so strong that the boiling point of sodium chloride is relatively high due to the large amount of energy required to break these bonds.
Since in a solid state atoms are bound tightly, electrons are not free to move about like in metallic bonds so when melted down into an aqueous solution the bonds are more loose allowing for electrons to move and conduction to occur.
Ionic compound are brittle due to the nature of their bonds. The sequence follows such that no two positive atoms or two negative atoms touch. Therefore if a column is shifted a single atom down resulting in two of the same charged atoms touching the object breaks due to the strong repulsion and is thus brittle in nature.