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

cbse
structureofatom

#1

${}{35}^{79}Br$ is not acceptable because atomic number should be written as subscript, while mass number should be written as superscript. ${}{35}Br$ is not acceptable because atomic number of an element is fixed. However mass number is not fixed as it depends upon the isotope taken. Hence, it is essential to indicate mass number.