An element has 20 protons and 20 neutrons. What is its atomic mass number?
Mass number = 20 + 20 = 40.
Ref: NCERT Class 11 Chemistry > Chapter 2: Structure of Atom > Topic: Discovery of Subatomic Particles - Electron Proton Neutron
#protons and neutrons
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Which of the following pairs represents isobars?
14C and 14N accurately defines or describes the concept asked in this question. Within Atoms and Molecules, precise definitions and terminology are essential for clear scientific communication. The other options (1H and 3H, 3H and 4He, and 140Ba and 140Th) either describe related but distinct concepts, use incorrect terminology, or confuse similar-sounding terms that have different scientific meanings. A thorough understanding of exact definitions helps distinguish between closely related biological concepts and is crucial for competitive examinations.
Ref: Campbell Biology, Urry et al., 12th Ed.
Which of the following statements about isotones is correct?
They have the same number of neutrons. is the scientifically accurate answer to this question. Within the study of Atoms and Molecules, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of They have the same number of neutrons. directly address what is being asked. Among the other options, They have the same number of protons., They have the same atomic number., and They have the same number of electrons. do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Campbell Biology, Urry et al., 12th Ed.