Tag: covalent bond

Graphite is an allotrope (a different structural form) of carbon (so is diamond), but unlike diamond, graphite can conduct electricity. The reason is that graphite consists of flat hexagons, all liked together in a flat plane. The carbons in the hexagons have delocalized pi bonding (pi bonds, along with a sigma bond, make up a double bond) which allows electrons to easily move from atom to atom making it a good conductor of electricity.

Graphite is a mineral made of loosely bonded sheets of carbon atoms, giving it a slippery texture that makes it a very effective lubricant. This slippery quality also makes graphite a good material for pencil lead because it easily sloughs off onto paper.

Covalent bond have weak intermolecular forces, that is to say, the forces between molecules is very weak. The consequence of this, is that it becomes easy to move individual molecules away from other molecules as the bonding between molecules is weak, hence it needs little energy to break. Since temperature is proportional to energy, that means the temperature required to melt the compound is low.
Thus option "A" is correct.

A covalent bond is formed between non metal atoms, which combine together by sharing electrons. covalent compounds have low melting points, do not dissolve in water, and do not conduct an electric current in solution that make them non-polar. 
Thus, Option "B" is correct.

The hydrogen bonds in an ice molecule are more apart than those in water molecules. Hence ice is loosely packed and is less densed than water. 

 Covalent bonds are directional, meaning that atoms so bonded prefer specific orientations relative to one another, hence they have distinct geometries.

Covalent compounds do not show ionic reaction. 

The increasing order of forces of attraction between the molecules can be written as;
$O _{2}$(weak Van der waal forces) < HCl( dipole-dipole interactions) < $H _{2}O$( hydrogen bonding) < Hg( metallic bond) < NaCl (ionic bonding)

A solid which is transparent to visible light and whose conductivity increases with temperature is
formed by covalent bonding, like a semi conductor.

Covalent compounds have negligible forces of attraction and these are gases e.g. $HCl$, sulfur dioxide,carbon dioxide and methane. There are weak forces of attraction and such covalent substances are low boiling temperature liquids such as ethanol so boils rapidly and gives off smell.