In a neutral atom, protons equal electrons, so there are 31 protons. Subtracting 31 protons from the mass number 70 gives 39 neutrons present in the nucleus of atom X.
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Rutherford’s accelerating electrons should radiate energy and collapse into the nucleus, causing atomic instability. Bohr resolved this by proposing that electrons revolve in discrete non-radiating orbits called stationary states, preventing atomic collapse.
Element a is Lithium Li with 3 electrons, 1 valence electron, valency 1 and atomic number 3. Element b is Carbon C with 6 electrons, 4 valence electrons, valency 4 and atomic number 6. Element c is Phosphorus P with ...
Magnesium contains 12 protons, 12 neutrons and 12 electrons. The 12 electrons are distributed across shells in the electronic configuration 2, 8, 2, placing two in K-shell, eight in L-shell and two in M-shell.
Option (ii) is the correct choice. Both statements are scientifically true, but the equality of protons and electrons explains electrical neutrality rather than providing the fundamental reason why discovering subatomic constituents clarified atomic architecture.