Question

What are the conditions necessary for the formation of covalent molecules?

Answer 1

As we know that the covalent molecules are formed between the molecules having covalent bonds and usually these molecules are the one having electronegativity difference. A chemical bond that involves the sharing of electron pairs leads to the formation of covalent bonds.

Complete answer:
To form a covalent molecule necessary conditions are required:
There must be a presence of valence electrons; it can be four or more than four valence electrons that are participating to form a covalent bond. The atoms that combine together to form a covalent bond must have equal electronegativity difference. There should be equal forces of attraction between combining atoms to form a covalent bond. The ionization energy for both the atoms must be high so that electrons cannot be easily removed. The approach of the atoms towards one another should be accompanied by decrease of energy.
Example of covalent molecule: hydrogen, oxygen, nitrogen
A covalent bond is formed when the electronegativity difference between the two atoms is too small $\left( { < 2} \right)$for electron transfer. Electronegativity is the ability of an atom to draw electrons to it. Atoms will covalently bond with other atoms to gain more stability, obtained by sharing the outermost (valence) electrons and forming a complete electron shell.

Note:
We need to know that the covalent bonds hold atoms together because the attraction between the positively charged nuclei and the negatively charged shared electrons is greater than the repulsions between the nuclei themselves. This attraction makes the molecules stable. The strength of a covalent bond is determined by the energy required to break it, that is, the energy necessary to separate the bonded atoms.