Question

The number of neutrons in dipositive zinc ion with mass number 70 is
(a) 34
(b) 36
(c) 38
(d) 40

Answer 1

Answer: (d) 40

Explanation:

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons

Atomic number is defined as the number of protons or number of electrons that are present in an atom for a neutral atom.

Atomic number = Number of electrons = Number of protons

For a positive ion: number of electrons = no of protons - positive charge

Atomic number of zinc is 30 and thus has 30 electrons. $Zn^{2+}$  is formed by loss of 2 electrons and thus has 28 electrons.

For $_{30}^{70}\textrm{Zn^{2+}}$

number of electrons = 30 - 2 = 28.

Mass number = Number of protons + Number of neutrons

70 = 30 + Number of neutrons

Number of neutrons  = 40

Thus number of neutrons in dipositive zinc ion with mass number 70 is 40.

Answer 2

Answer:

40

Explanation:

the correct configuration of N is

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