Multiple Choice
How many protons are present in an isotope of sodium with a mass number of 25?
160
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2. Atoms & Elements
Isotopes
Multiple Choice
An isotope of mercury has 80 protons and 120 neutrons. What is the mass number of this isotope?
A
120
B
200
C
80
D
160
Verified step by step guidance1
Identify the number of protons in the isotope, which is given as 80. The number of protons defines the element and is also called the atomic number.
Identify the number of neutrons in the isotope, which is given as 120. Neutrons contribute to the mass but do not affect the element's identity.
Recall that the mass number (\(A\)) of an isotope is the sum of the number of protons (\(Z\)) and neutrons (\(N\)): \(A = Z + N\).
Substitute the given values into the formula: \(A = 80 + 120\).
Add the numbers to find the mass number, which represents the total number of nucleons in the nucleus of the isotope.
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