Question

Symbol 79 35Br and 79 Be can be written, whereas symbol 35 79Br and 35Br are not acceptable.Answer briefly

Answer 1

Answer:

35Br79 is not acceptable because atomic number should be written as subscript, while mass number should be written as superscript. 35Br is not acceptable because atomic number of an element is fixed. However, mass number is not fixed as it depends upon the isotopes taken. Hence, it is essential to indicate mass number.

Explanation:

I hope you understand.

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.