Sodium Chloride is an alkali halide with an fcc crystal structure. The basis is two ions ... The cohesive energy of NaCl is - 7.90 eV, with a Coulomb contribution of -8.85 eV, a repulsive contribution ...
Elements bond in fixed ratios and so can be represented by a chemical formula. For example, sodium chloride has the same number of sodium ions and chloride ions, so its formula is NaCl ...