What is true of protons? they are positively charged and located inside the nucleus. they are positively charged and located outside the nucleus. they are negatively charged and located inside the nucleus. they are negatively charged and located outside the nucleus.

They are positively charged and located inside the nucleus.

Explanation:

An atom is smallest unit of a matter or substance.It consist of three subatomic particles : electrons, protons, neutrons.

Protons are positively charged and neutrons are neutral and both are located in the center of an atom where most of mass of an atom is concentrated and is called as nucleus.

Atomic mass = Number of protons + Number of neutrons

Electrons are negatively charged and are located outside the nucleus where they orbit in different energy levels around the nucleus.

Hence protons are positively charged and located inside the nucleus.

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.