Question

What is the mass number of an ion with 109 electrons, 159 neutrons, and a 1 charge?

Answer 1

It is not specified whether charge is +1 or -1.
If charge is +1, then total no. of electrons is 110,and so is atomic number.
Mass No.=No. of neutrons+ Atomic Number (1)
=159+110=269
If Charge is -1, total no.of electrons= 108= atomic number
From (1)
Mass No.= 159+108=267

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