Multiple Choice
An atom has 14 protons and 15 neutrons. Which element is it (and what is the isotope’s mass number)?
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4. Atoms and Elements
Isotopes
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Which statement best defines a radioactive isotope?
A
An isotope that has the same number of neutrons as protons in its nucleus
B
An isotope that cannot react chemically because its electrons are in a full valence shell
C
An isotope that has a net positive or negative charge due to gaining or losing electrons
D
An isotope with an unstable nucleus that spontaneously decays, emitting radiation
Verified step by step guidance1
Understand what an isotope is: isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
Recognize that a radioactive isotope, also called a radioisotope, is characterized by having an unstable nucleus.
Know that instability in the nucleus causes the isotope to spontaneously decay, which means it emits radiation in the form of particles or electromagnetic waves.
Distinguish radioactive isotopes from other types of isotopes, such as stable isotopes (which do not emit radiation) and ions (which have gained or lost electrons and carry a charge).
Conclude that the best definition of a radioactive isotope is an isotope with an unstable nucleus that spontaneously decays, emitting radiation.
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