Which particle is the only one that can be added or removed to create a charge

Electron

Explanation:

The electron is the only one that can be removed. Hope this helps :)

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.