Final answer:
The integer representing 9 electrons is -9, option A), as each electron carries a charge of -1.
Step-by-step explanation:
The integer that represents 9 electrons, each carrying a charge of -1, would be the sum of each individual electron's charge. Since each electron carries a negative unit charge of -1, we find that 9 electrons collectively have a charge of -9, corresponding to option A).
Protons and electrons are considered fundamental particles in atomic structure, with each proton carrying a positive charge of +1 and each electron carrying a negative charge of -1. It is important to note that charges in physics are quantified in terms of the Coulomb ('C'), and both protons and electrons have charges whose magnitudes are equal but opposite, specifically ±1.602 × 10-19 C.
Given that neutral atoms must have an equal number of protons and electrons, the atomic number effectively dictates the net charge. Thus, the charge of an isolated collection of electrons can be determined by simply multiplying the charge of a single electron by the total number of electrons, resulting in a negative integer for the collective charge.