Composition of the nucle of two atomi species x and Y are given in pic​

1. Mass number of X is 16, sum of proton and neutron i.e

8+8=16

And that of Y is:

10+8=18

2. Electronic configuration of both atoms is same as both have same atomic nmbr i.e 8 and we know that electronic configuration is based upon atomic number,

So electronic configuration is written:

1s2, 2s2, 2p4

3. They are related to each other by having same atomic numbers and same electronic configuration

Hope It helps