Number of electrons in nitrogen = 7
Number of electrons in oxygen = 8
We know that, the formula of nitrate ion is NO3-
We also know that number of electrons = (1× number of electrons in nitrogen ) + ( 3× number of electrons in oxygen ) + 1 =(1×7) + (3×8) + 1 = 32

Hence, the answer is 32

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Calculation of electrons in a nitrate ion

Nitrate ion is a polyatomic ion with a charge of -1. It is formed by the combination of one nitrogen atom and three oxygen atoms. Nitrogen atom has an atomic number of 7, which means that it has 7 protons and 7 electrons. Oxygen has an atomic number of 8, which means that it has 8 protons and 8 electrons.

Step 1: Calculation of electrons in nitrogen atom
Nitrogen atom has 7 electrons in its neutral state.

Step 2: Calculation of electrons in oxygen atom
Oxygen atom has 8 electrons in its neutral state.

Step 3: Calculation of electrons in nitrate ion
The nitrate ion is formed by the combination of one nitrogen atom and three oxygen atoms. The oxygen atoms donate a total of 6 electrons to the nitrogen atom, which already has 7 electrons. Therefore, the total number of electrons in a nitrate ion is:

7 + 6 = 13 electrons

Therefore, a nitrate ion has 13 electrons.

Explanation
The atomic number of an element is the number of protons in its nucleus. Since the number of electrons in an atom is equal to the number of protons, we can determine the number of electrons in an atom by knowing its atomic number. A nitrate ion is formed by the combination of one nitrogen atom and three oxygen atoms. Since oxygen is more electronegative than nitrogen, it can donate electrons to nitrogen to form a stable ion. The total number of electrons in a nitrate ion is the sum of the electrons in nitrogen and the electrons donated by oxygen.