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25 August, 15:55

An electrically neutral atom of gallium has 31 electrons and 39 neutrons. what is the mass number for an atom of gallium

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  1. 25 August, 16:08
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    Mass number = protons + neutrons.

    An electrically neutral atom has not formed an ion yet, so as of now, the number of electrons = number of protons.

    So, number of protons in gallium is = 31

    Thus, mass number = 31 + 39

    = 70.
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