Question

A nucleus of mass number 81 contains 46 neutrons. an atomic ion of this element has 36 electrons in it. write the symbol for this atomic ion (give the symbol for the nucleus and give the ionic charge as a right superscript).

Answer 1

A nucleus of mass number 81 contains 46 neutrons

Mass number=number of protons+number of neutrons

81=number of protons+ 46

number of protons=81-46

number of protons=35

In an atom, number of electrons=number of protons=35

So, the element is ⁸¹Br₃₅ .

Atomic ion of Br, having 36 electrons in it will be:

                                                                                      ⁸¹Br⁻₃₆

The symbol for this atomic ion will be Br and charge on the ion will be -ve.