Types of Solids and Chemical Bonds
Types of Solids and Their Properties
This table summarizes the properties of different types of solids:
| Type of Solid | Example Substance | Particles in the Crystal | Links Between Particles | Properties |
|---|---|---|---|---|
| Molecular | Simple substances or compounds of nonmetallic elements | Molecules (multimolecular structure) | Intermolecular forces | Low melting and boiling temperatures, not soluble in polar solvents. If polar, they may conduct in solution. If nonpolar, they will not conduct. |
| Giant Covalent | Diamond | Atoms (giant structure) | Covalent bonds | High melting temperature, hard but fragile, non-conductive, insoluble in all solvents. |
| Ionic | Binary compounds with a large difference in electronegativity | Positive and negative ions (giant structure) | Ionic bonds (electrostatic attraction between ions) | High melting temperature, fragile, non-conductive in solid state, but conductive when liquid or dissolved, soluble in polar solvents but not in nonpolar solvents. |
| Metallic | Metallic elements | Metal atoms | Metallic bonds | High melting point, hard but ductile and malleable, high density, good electrical conductor in solid and liquid states, insoluble in polar and nonpolar liquids. |
Chemical Bonds
Chemical bonds are the unions between atoms or ions to form molecules. Molecules, in turn, can be linked through intermolecular forces to form multimolecular structures:
- Ionic Bond: Occurs as a result of electrical forces between ions of opposite electric charge that form an ionic crystal.
- Covalent Bond: Arises between atoms that share a pair of electrons so that they generally complete their valence shell.
- Metallic Bond: Occurs as a result of electrical attraction between positive metal ions and the surrounding electron cloud. Properties: metallic luster, high density, high melting temperature and hardness, good electrical and thermal conductivity.
- Intermolecular Forces:
- Dipole-dipole forces: Are established between the positive dipole of one molecule and the negative part of the dipole of another.
- Dispersion forces: Are established between molecules due to the formation of instantaneous dipoles as a result of electron movement.
- Hydrogen bonds: Are established between the hydrogen atoms in a molecule and a small atom of high electronegativity (fluorine, oxygen, or nitrogen).
Additional Concepts
- Octet Rule: To form a molecule or giant structure, binding atoms tend to gain, lose, or share electrons to complete their valence shell with 8 electrons.
- Lewis Model: As two hydrogen atoms approach, electrostatic forces of attraction appear between the nucleus (proton) of one atom and the electron of the other, and repulsive forces appear between the two nuclei and the two electrons.
- Molecular Substances: Are formed by molecules that are held together by intermolecular forces. In the solid state, they form molecular crystals. Properties: They can be gaseous, liquid, or solid. Their melting and boiling temperatures depend on the intensity of these forces. They are soft and fragile, do not conduct electric current, and their solubility depends on polarity. Apolar molecular substances dissolve well in nonpolar solvents (e.g., turpentine). Polar molecular substances are soluble in polar solvents (e.g., water).
- Covalent Solids: Giant structures are formed by atoms of some elements such as boron, carbon, or silicon. These are linked through covalent bonds in a continuous network. Properties: High melting temperature, very hard, fragile, low conductivity, and insoluble. Examples include diamond, granite, and quartz.
- Ionic Solids: Networks are formed by giant structures of positive and negative ions. Their cohesion is due to electrostatic forces of attraction between oppositely charged ions. Properties: Very high melting temperature, high hardness, fragile, soluble, and do not conduct electricity in a solid-state. Examples: elements of groups 1 and 2 of the periodic table with elements of groups 16 and 17.