객관식
An isotope of yttrium has 39 protons and 59 neutrons. What is the mass number of this isotope?
148
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2. Atoms & Elements
Isotopes
객관식
Cadmium has eight naturally occurring isotopes. What do these isotopes have in common?
A
They all have the same mass number.
B
They all have the same number of neutrons.
C
They all have the same number of electrons and neutrons.
D
They all have the same number of protons.
검증된 단계별 안내1
Understand what an isotope is: Isotopes of an element have the same number of protons but differ in the number of neutrons.
Recall that the number of protons defines the element's identity and is called the atomic number.
Recognize that the mass number is the sum of protons and neutrons, so isotopes have different mass numbers.
Note that electrons can vary in ions, but isotopes specifically refer to atoms with the same proton count regardless of electrons.
Conclude that all isotopes of cadmium share the same number of protons, which is why they are all cadmium atoms.
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