Two atoms of element ‘M’ combine with 3 atoms of oxygen.
∴ Number of oxygen atoms combining with one atom of element ‘M’ =3\over2
Therefore, the valency of element ‘M’ = 3\over2 x 2= 3
Two atoms of element ‘M’ combine with 3 atoms of oxygen.
∴ Number of oxygen atoms combining with one atom of element ‘M’ =3\over2
Therefore, the valency of element ‘M’ = 3\over2 x 2= 3
| Elements | Protons | Electrons | Neutrons | Atomic Number | Mass Number |
| A | – | – | 10 | 8 | – |
| B | 15 | – | – | – | 31 |
| C | 1 | – | – | – | 3 |
| D | – | 11 | 12 | – | – |
| X | Y | |
| Protons | 8 | 8 |
| Neutrons | 8 | 10 |