How many atoms of one formula unit in Fe2O3

5 atoms form one formula unit of Fe2O3

Explanation:

2 atoms of Fe (Iron)

and 3 atoms of O ( Oxygen)

so total = 3 + 2

= 5

fe203 the right answer is thus

c is the answer because when something is left after something evaporates that shows the chemical change.

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.