One isotope of a nonmetallic element has mass num- ber 127 and 74 neutrons in the nucleus. The anion derived from the isotope has 54 electrons. Write the symbol for this anion.

I⁻

Explanation:

The identity of the element is obtained when the proton number is known.

Mass Number = 127

Neutrons = 74

Number of protons is obtained from;

Protons = Mass Number - Number of Neutrons

Protons = 127 - 74 = 53

The element is Iodine and it's symbol is I.

However, The anion derived from the isotope has 54 electrons

A neutral Iodine should have 53 electrons. This means it has gained a single electron. The symbol is now written as;

I⁻

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