Answer:
3 blue beads
1 red beads
4 green beads
Explanation:
The compound given:
        Ca₃PO₄
Elements in the compound are:
Ca
P
O
 Number of atoms are :
Ca - 3
P - 1
O Â - 4
blue beads to model Calcium
red beads to model Phosphorus
green beads to model Oxygen
  3 blue beads
  1 red beads
  4 green beads