Multiple Choice
In atomic theory, who is most commonly credited with developing the quantum mechanical (electron cloud) model of the atom?
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4. Atoms and Elements
Atomic Theory
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In atomic theory, how did Henry Moseley organize the periodic table compared with earlier arrangements?
A
By increasing atomic mass (average mass of isotopes)
B
By grouping elements strictly by physical state at room temperature (solid, liquid, gas)
C
By increasing atomic number (number of protons), which correlates with nuclear charge
D
By increasing number of neutrons in the most common isotope of each element
Verified step by step guidance1
Recall that before Moseley's work, the periodic table was primarily organized by increasing atomic mass, as done by Mendeleev.
Understand that Henry Moseley used X-ray spectra to determine the number of protons in the nucleus of an atom, which he called the atomic number.
Recognize that Moseley proposed organizing elements by increasing atomic number (number of protons) rather than atomic mass, which resolved inconsistencies in the earlier tables.
Note that organizing by atomic number better reflects the periodicity of chemical properties because the atomic number corresponds to the nuclear charge influencing electron arrangement.
Conclude that Moseley's arrangement improved the periodic table by providing a more accurate and consistent order of elements based on fundamental atomic structure.
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