For each of the following formulas, write the
name of each element and the number of atoms
of that element that are in the formula.

(a) 2k³po⁴

(b) 3al(oh)³

(c) 5fe²(so⁴)³

(a)  Potassium 3; phosphorus  1;       oxygen  4

(b) Aluminium 3;         oxygen  9;  hydrogen   9

(c)           Iron 10;            sulfur 15;      oxygen 60

Explanation:

(a) K₃PO₄

In one formula unit of K₃PO₄ , there are three atoms of potassium (K), one atom of phosphorus (P), and four atoms of oxygen (O).

In two formula units there are

  Potassium — six atoms

Phosphorus — two atoms

      Oxygen — eight atoms

(b) Al(OH)₃

In one formula unit of Al(OH)₃, there is one atom of aluminium (Al), three atoms of O, and three atoms of Hydrogen (H).

In three formula units there are

Aluminium — three atoms

    Oxygen — nine atoms

Hydrogen — nine atoms

(c) Fe₂(SO₄)₃

In one formula unit of Fe₂(SO₄)₃, there are two atoms of iron (Fe), three atoms of sulfur (S), and 12 atoms of O.

In five formula units there are

      Iron — 10 atoms

  Sulfur — 15 atoms

Oxygen — 60 atoms

law of conservation of matter