Question

how would you write 2molecules of Oxygen and 5molecules of nitrogen

Answer 1

It is written as
2 molecules of oxygen = 2Osubscript2
5 molecules of nitrogen = 5Nsubscript2
it is written like this because oxygen and nitrogen are diatomic molecule. Each oxygen and nitrogen molecule has 2 atoms respectively.

Answer 2

o=n-n-n-n-n=o
and 6 lone pair on each oxygen molecule