The opposite of an ordinary apple would be an anti-apple. Like an ordinary apple, the anti-apple would have a round shape, a stem, and a skin, but the electric charge of its particles would be reversed compared to those of an ordinary apple.

The anti-apple, also known as the antimatter apple, is a hypothetical concept based on the idea of antimatter. Antimatter is composed of subatomic particles that have the same mass as regular matter particles but carry opposite electrical charges. In the case of the anti-apple, it would have negatively charged protons, negatively charged electrons, and positively charged neutrons. Visually, the anti-apple would bear a strong resemblance to a regular apple. It would have a round shape, a stem protruding from the top, and a smooth skin. The coloration and other physical attributes, such as size and texture, would be the same as an ordinary apple. However, due to its opposite electrical charge, interactions between the anti-apple and ordinary matter would lead to annihilation. When an anti-apple collides with a regular apple or any other matter, the opposite charges would neutralize each other, resulting in a release of energy. This annihilation process is part of the equation you mentioned, where the collision of electric charges sums up to 0. It's important to note that as of now, antimatter apples do not exist in reality, and their properties are largely based on theoretical considerations within the realm of particle physics.