What are the respective central-metal oxidation state, coordination number, and overall charge on the complex ion in Na2[Cr(NH3)2(NCS)4]? A) +3; 6; -1
B) +2; 6; -2
C) +1; 6; -2
D) +3; 6; +1

B) +2; 6; -2

Explanation:

In order to know what the coordination number is, all we need to do is to count the number of ligands present in the coordination sphere. Coordination number refers to the number of ligands in the coordination sphere of a given complex. The coordination number here is 6.

The counter ion here is 2Na+. It means that the overall charge on the complex must be -2 because the magnitude of charge on the complex ion is exactly balanced by the number of counter ions.

The charge on the metal (x) must now be;

x + 0 + 4(-1) = -2

x - 4 = -2

x = -2 + 4

x = +2

Note that NH3 is designated as zero because it is a neutral molecule. Each NCS^- ion has a charge magnitude of -1.

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.

the answers are

c and c