Question

Check image for the question and answer briefly.

Answer 1

because the symbol BR 7935 and BR 79 ad Universe University accepted symbol and therefore symbol by br3579 is not accepted because always the mass number is written above and the atomic number below that is mass number in a superscript and atomic no. in subscript

Answer 2

Answer:

This is because, the general form of representing elements if of the form of:

$\ce{ ^{A}_{Z} X }$

Here,

A represents Atomic Mass, Z represents Atomic Number and X represents Symbol of the Element.

This is the general form accepted universally.

But in the second part of question, in the place of mass number, atomic number is written. Due to this it leads to misconception that both are interchanged and hence it is wrong way of representing.

Hence the second two ways are wrong while the first two ways are correct.

Hope my answer helped !