Ionic Compounds
Electrical Conductivity: Ionic compounds can conduct electricity, but only when they are melted into a liquid (molten) or dissolved in water (aqueous solution). This is because their ions, which carry electrical charge, are free to move around in these states. In their solid form, the ions are stuck in place and cannot move, so they do not conduct electricity.
Melting and Boiling Points: Ionic compounds usually have very high melting and boiling points. This is because the positive and negative ions in these compounds are held together by strong forces of attraction called electrostatic forces. A lot of heat energy is needed to overcome these strong forces and separate the ions.
Solubility in Water: Most ionic compounds dissolve easily in water. Water is a polar substance, meaning its molecules have slightly positive and negative ends. These ends attract the positive and negative ions in the compound, pulling them apart and keeping them separate in solution.
Physical State: At room temperature, most ionic compounds are hard solids. They form neat, repeating patterns of ions, which are called crystal lattices. These give the compounds their solid structure.
Brittleness: Ionic compounds are brittle, which means they can easily break or shatter when struck. This happens because when layers of ions are pushed, ions with the same charge may come close together and repel each other, causing the structure to break apart.
Covalent Compounds
Electrical Conductivity: Covalent compounds usually do not conduct electricity. This is because they do not have free-moving charged particles like ions or electrons. The electrons are tightly shared between atoms in the molecule and cannot move freely.
Melting and Boiling Points: Covalent compounds often have low melting and boiling points. This is because the molecules are held together by weak forces called intermolecular forces. It doesn’t take much heat to overcome these forces and change the compound from solid to liquid or liquid to gas.
Solubility in Water: The solubility of covalent compounds in water depends on whether they are polar or non-polar. Polar covalent compounds can dissolve in water because they have slightly charged ends that attract water molecules. Non-polar compounds usually don’t dissolve in water because they do not mix well with the polar nature of water.
Physical State: Covalent compounds can be found in all three states at room temperature—some are gases (like oxygen), some are liquids (like water), and others are soft solids (like wax). Their state depends on how strongly the molecules are held together.
Bond Type and Structure: Covalent compounds are made up of small molecules where atoms are connected by covalent bonds—this means they share electrons. These shared electrons create a strong connection within each molecule, but each molecule remains a separate, independent unit.