Question

Symbols $^{79}_{35}Br$ and $^{79}Br$ can be written whereas symbols $^{35}_{79}Br$ and $^{35}Br$ are not acceptable. Answer briefly.

Answer 1

mate I am very weak in mathematics

Answer 2

$\textcolor{red}{Answer :-}$

An atomic number of an element should always be written as a sub script on the left side of the element while the mass number is written as a superscript on the same side as the atomic number.

In the first case of the given question, Br can be written in both ways as it follows the correct positioning of atomic number and mass number.

But, in the second case, firstly, atomic number and mass number are positioned in this way : $^{35}_{79}Br$

Hence, it is clear that that their actual positions are interchanged i.e., atomic number is written as superscript and mass number as subscript. So, it is invalid.

And secondly, atomic number is positioned wrongly as superscript (in the place of mass number) : $^{35}Br$.

Hence, this way is also not acceptable as atomic number is fixed of all elements but their mass numbers depends upon the isotope of the element taken.