Someone how do the number of electrons in the second energy shell of an atom change going across period 2 in the periodic table? a. the number of electrons increases by 1, from left to right. b. atoms in period 2 do not have a second energy shell, instead the first energy shell increases in electrons from left to right. c. the number of electrons in the second energy shell is full, the number of electrons in the third energy shell increase by 1. d. the number of electrons increases by 1, from right to left.

what is the question?

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.