Multiple Choice
In atomic structure, how is the mass number of an atom calculated?
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4. Atoms and Elements
Isotopes
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In terms of subatomic particles, how does one isotope of an element differ from another isotope of the same element?
A
They have different numbers of electrons but the same number of protons.
B
They have different numbers of protons but the same number of neutrons.
C
They have different chemical symbols because they are different elements.
D
They have different numbers of neutrons but the same number of protons.
Verified step by step guidance1
Recall that an element is defined by its number of protons, also called the atomic number (Z). This number is unique to each element and does not change between isotopes of the same element.
Understand that isotopes of an element have the same number of protons but differ in the number of neutrons. Neutrons contribute to the atomic mass but do not affect the chemical identity of the element.
Recognize that electrons can vary in ions but do not define isotopes. Isotopes focus on differences in neutrons, not electrons.
Note that the chemical symbol remains the same for isotopes of the same element because the number of protons (and thus the element identity) is unchanged.
Summarize that isotopes differ by their neutron count while having the same proton count, which explains why they have different mass numbers but the same chemical properties.
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