 Crystalline solids cohesion is obtained by a metallic or chemical bond which is formed between the constituent atoms . Chemical bonds can be grouped into two types consisting of ionic and covalent . To form an ionic bond , either a valence or bonding electron separates from one atom and becomes attached to another atom to form oppositely charged ions . The bonding in the static position is when the ions occupy an equilibrium position where the resulting force between them is zero . When the ions are exerted in tension force , the inter @-@ ionic spacing increases creating an electrostatic attractive force , while a repulsing force under compressive force between the atomic nuclei is dominant . 
