Which of the following statements is incorrect about covalent network solids?
They are formed by the covalent bonding between atoms
They have high melting and boiling points due to strong covalent bonds
They are usually brittle and hard
They have a regular arrangement of atoms in a three-dimensional structure
Covalent network solids, also known as atomic solids, are solids that are held together by a network of covalent bonds. Unlike ionic solids, where there is a transfer of electrons between atoms, in covalent network solids, the electrons are shared between atoms to form a continuous network. This results in a strong and stable three-dimensional structure that is difficult to break.
Option a) is correct since covalent network solids are formed by the covalent bonding between atoms. Option b) is also correct because the covalent bonds in these solids are very strong, resulting in high melting and boiling points. The strong bonds make it difficult to break the network, requiring a significant amount of energy to overcome the forces holding the atoms together.
Option c) is incorrect because covalent network solids are not usually brittle and hard. Instead, they are often very hard and have a high degree of rigidity. Examples of covalent network solids include diamond, silicon carbide, and quartz. Diamond, for instance, is one of the hardest naturally occurring substances and is used in cutting tools and jewelry. These solids are so hard and rigid that they can scratch or wear away even some of the strongest materials.
Option d) is also correct because covalent network solids have a regular arrangement of atoms in a three-dimensional structure. The arrangement is often repeated throughout the solid, resulting in a crystal lattice structure.
In summary, option c) is incorrect since covalent network solids are not usually brittle and hard, but rather they are often very hard and rigid.