The number of covalent bonds that an atom tends to form is equal to:

a: the number of valence electrons.

b: the number of unbalanced neutrons.

c: the number of unpaired electrons.

d: the atomic number.

e: the number of nearby atoms.

A). the number of valence electrons.

Explanation: Atom has certain numbers of valence electrons, which developed bonds in order to complete their valence shell. In a neutral atom the number of bonds is equal to the number of electrons in the valence shell minus the number of valence electrons. This technique is useful in order to attain an atom valence shell without changing its charge when it form covalent bond and add another electron in its valence shell.

Example:

Number of bonds =  (Whole valence shell) - ( Amount of valence electron)

For hydrogen

        1                     =               2                       -                1

For carbon

         4                    =              8                       -                4

the answer is c.) there is a warm front in region a and a stationary front in region b.