Symbols \,{^{79}₃5}Br} and \,{^{79}Br} can ...

NCERT Class XI Chemistry Structure of Atom Solutions

Question : 41 of 67

Marks: +1, -0

Symbols

\,\mathrm{^{79}_{35}Br}

and

\,\mathrm{^{79}Br}

can be written, whereas symbols

\,\mathrm{^{35}_{79}Br}

and

\,\mathrm{^{35}Br}

are not acceptable. Answer briefly.

Solution:

Atomic number should be a subscript while mass number should be a superscript of the symbol of an element. Thus,

\,\mathrm{^{35}_{79}Br}

is not acceptable. The atomic number is fixed, but different isotopes of bromine atoms may have different mass numbers. Therefore, it is essential to mention mass number.

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