Question
Predict the elements corresponding to the following numbers of protons and neutrons.
A: 20 protons and 20 neutrons
B: 19 protons and 20 neutrons
Asked in RRB Group D · 2025
Modern Periodic Table · Chemistry
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Mendeleev arranged elements mainly by atomic mass and recurring properties.
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Modern Periodic Table: Groups, Periods & Blocks has appeared in 43 previous-year exam questions, most frequently in UPSC, State PSC and SSC.
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