Achromate ion consists of four oxygen atoms bonded to a chromium atom. it has two extra electrons. the formula of this ion:

cr4o2–

cro42+

cro42– (this one is correct by the way)

The correct answer is

Explanation:

Chromate ion is formed by the combination of one chromium atom and four oxygen atoms. The ion formed has two more electrons.

An ion which has extra electrons carries a negative charge on them and the ion which has more electrons carries a positive charge on them.

As, chromate ions have 2 extra electrons, Thus, it carries a charge of -2.

Hence, the correct answer is

the answer is barium and copper bromide

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.