Question

Covalent compounds are generally liquids or gases. Explain.

No short answers !! ^-^

Answer 1

Covalent compounds are formed by covalent bonds. Covalent bonds are formed by sharing of electrons. Due to this bond strength is comparatively weak than ionic compounds.

In a covalent compound, the bond strength between atoms are strong. But the Inter molecular force of attraction is less. Due to this they have low melting points and boiling points.

Since low melting points are mostly between the room temperature, the covalent compounds exist as liquids in room temperature. Some compounds have low boiling points also less than room temperature. Hence they exist as gases.

Exceptions are Diamond which is a covalent compound having high melting and boiling point. This is because in diamond the inter molecular force of attraction between carbon is strong enough to remain intact. Hence they need high energy for breaking bond. Due to high Bond disassociation energy they have high melting and boiling point.

Answer 2

The atoms can be of the same element or different elements. In each molecule, thebonds between the atoms are strong but thebonds between molecules are usually weak. ...Compounds with covalent bonds may besolid, liquid or gas at room temperature depending on the number of atoms in the compound.

PROPERTIES:

Covalent compounds usually have low melting points except in case of molecules like diamonds and silica latticeThe boiling points of these covalent molecules is low as the force of attraction between the bonded atoms are held together by van der Waal forcesCovalent bonded compounds are usually gases and liquids with low boiling and melting pointsCovalent compounds which are solids are either have soft structures like graphite as there is a cloud of electrons in between each layer of carbonsThe covalent compounds are non-conductors of electrical charge as there are no charged ions in covalent molecules except in case of graphite where we get to see cloud of electrons which help in the conductionCovalent compounds are bad conductors of heat energy as well, as these molecules lack free electrons which eventually provides infinite resistance to flow of heat energy.Conduction of heat does not bring in any changes in metals as they have free electrons to carry these energy but in case of covalent compounds these result in complete combustion as the molecules do not allow free passage of either electrical charge and heat energy and hence bring in the chemical changeCovalent compounds do not possess polar characteristics as a general property and hence are not soluble in water. Water molecules are not absolutely neutral and have a slight negative charge on the oxygen atom and slight positive charges on the hydrogen atoms and since covalent compounds are made up of neutral molecules or molecules with slight charges and hence are not attracted to water molecules strongly.