The tendency of an element to react is closely related to

Answer: The tendency of an element to react is closely related to the number of valence electrons in the element.

Explanation:

Chemical reactivity is defined as the tendency of an element to loose of gain electrons.

Metals tend to loose electrons and so their chemical reactivity is the tendency to loose electrons.

Non-metals tend to gain electrons and so their chemical reactivity is the tendency to gain electrons.

The number of electrons that an element will loose or gain depends on the number of valence electrons present around that element.

For Example: Chlorine has 7 valence electrons and need 1 electron to complete its octet, whereas sulfur has 6 valence electrons and need 2 electrons to complete its octet.

So, chlorine will gain 1 electron easily than sulfur and thus, is more reactive than sulfur.

Hence, the tendency of an element to react is closely related to the number of valence electrons in the element.