Question

The formula for aluminum fluoride is electrically neutral. Which of the following is the correct formula for this compound? Which consists of only aluminum and fluoride ions? An aluminum ion has three positive charges

Answer 1

In aluminium fluoride, aluminium carries positive charges so fluoride should carry negative charge to be electrically neutral.So for aluminium ion with three positive charges fluoride ion should possess three negative charges to make aluminium fluoride electrically neutral.

$AlF_{3}$→$Al^{3+} and F^{3-}$