Final answer:
The highly ordered atomic structure in solids is called crystalline, while the disordered structure is termed amorphous. Crystalline solids have uniform particle arrangements with distinct melting temperatures, whereas amorphous solids have a range of particle interactions and gradual melting points.
Step-by-step explanation:
A solid that has a highly ordered structure at the atomic level is referred to as a crystal, whereas solids with a relatively disordered structure are described as amorphous.
Therefore, the correct answer to the question is option a) Crystal;
Amorphous. Crystalline solids have a regular, repeating three-dimensional structure, like that of NaCl, which consists of a regular array of Na+ ions and Cl- ions.
On the other hand, amorphous solids lack this long-term structure and consist of molecules with no specific order from one to the next, such as glass or many plastics.
In contrast, amorphous solids experience a range of interactions leading to a gradual softening and melting over a range of temperatures.
Understanding these differences is important for applications like creating semiconductors where controlled crystalline defects can affect properties like electrical conductivity.