Multiple Choice
An atom has 38 protons and 50 neutrons. What element is it (and what isotope is specified by these numbers)?
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4. Atoms and Elements
Isotopes
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Which of the following represents an isotope of lithium (Li)?
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Verified step by step guidance1
Understand that isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
Identify the element lithium (Li) by its atomic number, which is the number of protons. Lithium has an atomic number of 3.
Look at the given options and check their atomic numbers (the lower number in the isotope notation). The isotope must have an atomic number of 3 to be lithium.
Compare the mass numbers (the upper number in the isotope notation) of the lithium isotopes. Different mass numbers indicate different numbers of neutrons, which means they are isotopes of lithium.
Exclude any options that have a different atomic number, as they represent different elements, not isotopes of lithium.
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