How does an atom end up with an octet, if it loses all of the electrons in its valence shell

When atoms have fewer than eight electrons, they have an inclination to react and type a lot of stable compounds.

Thus, associate atom continues to create bonds till associate octet of electrons is formed. this can be called octet rule by Lewis.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.