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Atomic Structure revision notes

Every idea in the Atomic Structure chapter for JEE Main, with the usual mistakes and the fast methods. Topic 1 is open to everyone; sign in free to read all 25 and download the PDF.

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Subatomic particles and early models

Atomic notation and isoelectronic species
6× asked, last 2026
ZAX:neutrons=A−Z,electrons=Z−(ion charge){}^{A}_{Z}\mathrm{X}:\quad \text{neutrons}=A-Z,\qquad \text{electrons}=Z-(\text{ion charge})
Bottom ZZ = protons, top AA = protons + neutrons. Isotopes: same ZZ; isobars: same AA; isotones: same neutrons.
  • Isoelectronic = equal electron count, whatever the charge. 10: NX3−\ce{N^{3-}}, OX2−\ce{O^{2-}}, FX−\ce{F-}, NaX+\ce{Na+}, MgX2+\ce{Mg^{2+}}, AlX3+\ce{Al^{3+}}. 18: SX2−\ce{S^{2-}}, ClX−\ce{Cl-}, KX+\ce{K+}, CaX2+\ce{Ca^{2+}}, ScX3+\ce{Sc^{3+}}.
Electron, proton and neutron
4× asked, last 2023
e=1.602×10−19 C,me=9.109×10−31 kg,e/me=1.76×1011 C kg−1e = 1.602\times10^{-19}\ \text{C},\qquad m_e = 9.109\times10^{-31}\ \text{kg},\qquad e/m_e = 1.76\times10^{11}\ \text{C kg}^{-1}
Proton: charge +e+e, about 1836 times mem_e. Neutron: no charge, slightly heavier than the proton.
Also remember
  • Dalton's postulates: matter is made of indivisible atoms; an element's atoms are identical, mass included; different elements' atoms differ in mass; compounds form in fixed simple ratios; reactions only rearrange atoms.

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Practise Atomic Structure

23 more concepts in 6 topics

Electromagnetic radiation and the photon, Bohr model of hydrogen-like species, Hydrogen spectrum, Dual nature and uncertainty, Quantum-mechanical model and orbitals and Orbital energies and electronic configuration. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Electromagnetic radiation and the photon

  • Wave relations4×
  • Planck's quantum: photon energy11×
  • Photoelectric effect11×
  • Also remember1

Bohr model of hydrogen-like species

  • Bohr's postulates and limits4×
  • Radius of the nth orbit9×
  • Energy and ionisation energy9×
  • Speed, KE and PE5×

Hydrogen spectrum

  • Rydberg formula10×
  • Series, first line and limit13×
  • Number of spectral lines2×
  • Also remember1

Dual nature and uncertainty

  • de Broglie wavelength9×
  • de Broglie wave in a Bohr orbit5×
  • Heisenberg uncertainty principle9×

Quantum-mechanical model and orbitals

  • Quantum numbers11×
  • Counting orbitals and electrons10×
  • Orbital angular momentum2×
  • Nodes13×
  • ψ and ψ² for 1s and 2s8×
  • Shapes of p and d orbitals4×

Orbital energies and electronic configuration

  • Energies of orbitals14×
  • Aufbau, Pauli and Hund9×
  • Exceptional configurations11×
  • Configurations of ions9×

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Practise Atomic Structure

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