Short answers, pulled from the story.
Ionic bonding is a type of chemical bonding driven by the electrostatic attraction between oppositely charged ions, or between two atoms with sharply different electronegativities. It is the primary interaction in ionic compounds and is one of the main bonding types alongside covalent and metallic bonding.
When sodium and chlorine combine, each sodium atom loses an electron to become a Na+ cation and each chlorine atom gains an electron to become a Cl minus anion. These ions are attracted to each other in a one to one ratio to form sodium chloride, NaCl, common table salt.
Ionic compounds lose their crystal lattice structure and break up into free ions when dissolved in water or other polar solvents, a process called solvation, or when heated above their melting point. These free ions allow molten and aqueous ionic compounds to conduct electricity, while solids typically do not.
No, clean ionic bonding in which one atom completely transfers an electron to another cannot exist, because the proximity of the entities allows some sharing of electron density. All ionic compounds have some degree of covalent character, so a bond is called ionic only when its ionic character is greater than its covalent character.
The strength of a solid ionic compound is measured as its lattice energy, the enthalpy change in forming the solid from gaseous ions, determined experimentally using the Born-Haber cycle. It can also be calculated with the Born-Lande equation, and ionic bond strengths typically fall between 170 and 1500 kJ/mol.
In ionic bonding atoms are held together by the attraction of oppositely charged ions and pack according to maximum packing rules, while in covalent bonding atoms share electrons and follow VSEPR geometry. Ionic bonding allows higher coordination numbers, such as 6 in NaCl and 8 in CsCl, whereas carbon typically forms a maximum of four bonds.