How is a sodium ion symbol written? so so- na na-

   Na⁺ or Na⁺¹

Explanation:  Sodium as an element of the first group of the periodic system has atomic number 11. This means that there are 11 electrons negatively charged around the nucleus, and also 11 protons in the nucleus that are positively charged. As is known, the number of electrons and protons should be equal within the element to keep the element neutral. In order for the sodium element to become a sodium ion, one electron leaves its place and has 10 electrons, which is one less than the number of protons in the nucleus, so that the sodium ion is positive. The ion symbol is written by adding the superscript on the right as + or - in addition to the symbol of the element that is first written, depending on which ion is in question. In this case, + should be written as a superscript.

Also if the charge of the ion is say, +2 then it is written as a superscript behind the element symbol as +2. If it is +1 like with sodium ion, then only + can be written.

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 answer is d.) potassium