Question

how can the maximum number of electrons that can be accommodated in the outermost orbit is eight ????

Answer 1

This is due to the filling of electrons under "aufbau principle or rule",
 also known as the "diagonal rule".

Answer 2

Answer:

The outermost shell in an atom cannot have more than eight electrons even if it has a capacity to take up more electrons. This is also called the octet rule.