Question

Examine the three isotopes of potassium (K) below.

potassium-41, potassium-39, potassium-40

Which answer choice lists these isotopes in the order of having the least amount of neutrons to having the most amount of neutrons?

potassium-41, potassium-39, potassium-40
potassium-39, potassium-41, potassium-40
potassium-39, potassium-40, potassium-41
potassium-41, potassium-40, potassium-39

Answer 1

Answer: The correct answer is Potassium-39, Potassium-40, Potassium-41

Explanation:

Atomic number is defined as the number of protons present in an atom.

Mass number is defined as the sum of number of protons and number of neutrons present in an atom. It is represented as A.

A = Mass number = Number of neutrons + Number of protons.

For the given isotopes of potassium:

Atomic number of potassium is 19.

For potassium-41 isotope:

Mass number = 41

Number of neutrons = 41 - 19 = 22

For potassium-39 isotope:

Mass number = 39

Number of neutrons = 39 - 19 = 20

For potassium-40 isotope:

Mass number = 40

Number of neutrons = 40 - 19 = 21

The most number of neutrons are in potassium-41 isotope and the least number of neutrons are in potassium-39

Hence, the correct answer is Potassium-39, Potassium-40, Potassium-41