An atom of potassium is represented by the nuclide symbol ^{39}_{19}\text{K}. How many neu… — JAMB UTME

An atom of potassium is represented by the nuclide symbol $^{39}_{19}\text{K}$ . How many neutrons are present in the nucleus of this atom?

The nucleus of the potassium atom contains 20 neutrons.

The correct answer is 20 because the number of neutrons in an atom is found by subtracting the atomic number (19) from the mass number (39), giving

39 - 19 = 20

Identify the mass number (

A

) and atomic number (

Z

) from the given nuclide notation

^{39}_{19}\text{K}

Mass number

A = 39

, Atomic number

Z = 19

In standard nuclide notation

^{A}_{Z}\text{X}

, the superscript represents the mass number and the subscript represents the atomic number.

Calculate the number of neutrons (

N

) using the relationship

N = A - Z

N = 39 - 19 = 20

The mass number is the sum of protons and neutrons (

A = Z + N

), so subtracting the atomic number (protons) from the mass number gives the neutron count.

Mass Number and Subatomic Particles

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