Polar molecular solids, such as sugar, dissolve easily in water. These nonpolar molecular solids will not dissolve in water, but will dissolve in a nonpolar solvent, such as benzene and octane. This electrostatic attraction between the two poles (dipoles) is much weaker than ionic or covalent bonding, so molecular solids tend to be softer than ionic crystals and have lower melting points (many will melt at less then 100 C, or 212 F). Because covalent bonding involves sharing electrons rather than outright transfer of those particles, the shared electrons may spend more time in the electron cloud of the larger atom, causing weak or shifting polarity. Molecular solids are composed of covalently bonded molecules attracted to each other by electrostatic forces (called van der Waals forces, according to the HyperPhysics website). Polyatomic ions are groups of atoms that share electrons (called covalent bonding) and function in a compound as if they constituted a single charged ion. They may also be composed of polyatomic ions such as NH 4NO 3 (ammonium nitrate). They may be simple binary salts like sodium chloride (NaCl), or table salt, where one atom of a metallic element (sodium) is bonded to one atom of a nonmetallic element (chlorine). While the crystals themselves are hard, brittle and nonconductive, most ionic compounds can be dissolved in water, forming a solution of free ions that will conduct electricity. This means that ionic compounds have very high melting points, often between 300 and 1,000 degrees Celsius (572 to 1,832 degrees Fahrenheit). Because of the strong attraction between opposite charges, it takes a lot of energy to overcome ionic bonds. Ionic compounds form crystals that are composed of oppositely charged ions: a positively charged cation and a negatively charged anion. There are four types of crystalline solids: ionic solids, molecular solids, network covalent solids and metallic solids.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |