Ontario Grade 9 Science Class Practice Exam

An ion is a particle that has either a positive or negative charge. Option A is incorrect because a neutral particle does not have a charge. Option B is also incorrect because a positive charge alone does not make a particle an ion. Option D is incorrect because a particle with both a positive and negative charge would cancel out and result in a neutral particle. Therefore, the correct answer is option C, as it accurately describes the concept of an ion having a charge of either polarity.