Multiple Choice
One isotope of sodium has 11 protons and 7 neutrons. What is the mass number of this isotope?
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2. Atoms & Elements
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Struggling with General Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
How many neutrons are present in an atom of potassium-39?
A
20
B
19
C
21
D
18
Verified step by step guidance1
Identify the atomic number of potassium (K) from the periodic table, which is 19. This number represents the number of protons in the atom.
Determine the mass number of the potassium isotope given in the problem, which is 39. The mass number is the sum of protons and neutrons in the nucleus.
Use the formula: \( \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \).
Substitute the known values into the formula: \( \text{Number of neutrons} = 39 - 19 \).
Calculate the result to find the number of neutrons in an atom of potassium-39.
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