Which atomic number is the threshold value below which fusion may occur?

The atomic number 26(iron) is the threshold value below which the fusion might occur.

Explanation:

Nuclear fusion is a reaction in which two or more nuclei are combined to form one or more different atomic nuclei and subatomic particles.

Energy released in a fusion reaction is because of a key feature of nuclear matter called the binding energy which is a measure of the efficiency with which its constituent nucleons are bound together.

As we go up in atomic number, the energy released per nuclei goes down until it hits a minimum which is for atomic number 26 (iron) and fusion is not possible.

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.