Final answer:
The positive ion in calcium phosphide is calcium (Ca²+), the negative ion is phosphide (P³−), and the formula for calcium phosphide is
which represents a neutral compound with balanced charges.
Step-by-step explanation:
The positive ion in calcium phosphide is calcium (Ca²+), and the negative ion is phosphide (P³−). To achieve an electrically neutral compound, three calcium ions are needed to balance two phosphide ions due to their charges. The least common multiple of 2 and 3 is 6, which tells us we need equal amounts of positive and negative charge to cancel out. Thus, we get three Ca²+ ions providing a 6+ charge and two P³− ions providing a 6− charge. The correct formula for calcium phosphide is