Chemistry

Triple covalent bond :
A triple covalent bond is formed when three pairs of electrons (six electrons) are shared between the two combining atoms. A triple bond is shown by marking three short lines between the two symbols of the atoms.
EXAMPLES :
1. Formation of a nitrogen molecule (N₂) :
An atom of nitrogen has five electrons in its valence shell. It requires three more electrons to attain the stable octet. This is achieved when two nitrogen atoms combine together by sharing three electrons each to form a nitrogen molecule.

Pictorially, a nitrogen molecule can be represented as in figure

Formation of an acetylene molecule (C₂H₂) :
In an acetylene molecule, two C atoms combine with two H atoms. Each C atom shares three of its valence electrons with the other C atom. One electron of each C atom is shared with one electron of a H atom.
Thus, in a molecule of acetylene, there is a triple covalent bond between the two C atoms and each C atom is joined to one H atom by a single covalent bond. Pictorially, a molecule of acetylene may be represented as in figure.

Characteristics of covalent compounds :
1. Covalent compounds are made up of neutral molecules. Hence, the forces of attraction between the molecules are weaker than those found in ionic compounds. Therefore, covalent compounds are usually volatile liquids or gases.
2. The melting and the boiling points of covalent compounds are generally low. Since covalent compounds are made up of neutral molecules, the forces of attraction between the molecules are very weak. So, a comparatively small amount of heat energy is required to break these weak intermolecular forces of attraction. Hence, they have low melting and boiling points.
3. Covalent compounds are insoluble in water but soluble in organic solvents.
4. Covalent compounds do not conduct electricity. This is because they are made up of neutral molecules, not ions, and do not produce ions in the molten state or in aqueous solutions.