Atomic No. | Mass No. | Valency | |
X | 5 | 11 | 3 |
Y | 8 | 18 | 2 |
Z | 15 | 31 | 3, 5 |

Atomic No. | Mass No. | Valency | |
X | 5 | 11 | 3 |
Y | 8 | 18 | 2 |
Z | 15 | 31 | 3, 5 |
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 |