Science · X-Factor Notes
Atomic Structure revision notes for UPPCS Prelims.
High-Yield Revision| Concept | What to remember | Asked in UPPCS |
|---|---|---|
| Electron | It is a negatively charged sub-atomic particle (e- ). It carries a charge of - 1.6022 x 10-19 coulomb. Its mass is approximately 1/1837 that of the proton. | U.P. R.O./A.R.O. (Pre) 2023 |
| Discovery of Electron | Discovered by J.J. Thomson in 1897. | U.P. R.O./A.R.O. (Pre) 2023 |
| Proton | It is a positively charged sub-atomic particle (p or p+). It carries a charge of - 1.6022 x 10-19 coulomb. | U.P. R.O./A.R.O. (Pre) 2023 |
| Discovery of Proton | First discovered by Goldstein as anode rays (1886) and finally identified and named by Rutherford (1919). | U.P. R.O./A.R.O. (Pre) 2023 |
| Neutron | It is a neutral sub-atomic particle (n or n), slightly heavier than the proton (mass 1.0087 amu). | U.P. P.C.S. (Pre) 1996, U.P. P.C.S. (Pre) 1995, U.P. R.O./A.R.O. (Pre) 2023 |
| Discovery of Neutron | Discovered by James Chadwick in 1932. | U.P. P.C.S. (Pre) 1996, U.P. P.C.S. (Pre) 1995, U.P. R.O./A.R.O. (Pre) 2023 |
| Atomic Nucleus | The small, dense, positively charged region at the center of an atom, consisting of protons and neutrons (nucleons). Electrons revolve around the nucleus. | U.P. R.O./A.R.O. (Mains) 2017 |
| Discovery of Nucleus | Discovered by Ernest Rutherford in 1911. | |
| Deuteron | Contains a proton and a neutron, but is not considered a sub-atomic particle. | U.P. P.C.S. (Pre) 2007 |
| Atom Neutrality | An atom is electrically neutral because the number of electrons (negative charges) equals the number of protons (positive charges). | |
| Photon | Associated with light energy (energy packet of light) and is not considered a part of the atom. | |
| Particle-Antiparticle Pair | Electron and Positron constitute a particle-antiparticle pair. | U.P. P.C.S. (Mains) 2005 |
| Concept | What to remember | Asked in UPPCS |
|---|---|---|
| Atomic Number (Z) | Defined as the number of protons in the nucleus. It is the fundamental characteristic of a chemical element. | |
| Mass Number (A) | The total number of nucleons (protons + neutrons) in the nucleus. It is approximately equal to the atomic weight. | |
| Mass Number Calculation |
| Concept | What to remember | Asked in UPPCS |
|---|---|---|
| Radioactivity | A nuclear phenomenon where an unstable atomic nucleus loses energy by spontaneously emitting radiation. Discovered by Henri Becquerel (1896). | U.P. P.C.S. (Pre) 2021, U.P. R.O./A.R.O. (Mains) 2016, U.P. P.C.S. (Mains) 2003 |
| Alpha Particles | Positively charged particles, nuclei of helium 24He++. Deflected towards the negative charged plate. | |
| Isotopes | Atoms of the same element (same number of protons) that have different mass numbers (A) due to different numbers of neutrons. | U.P. P.C.S. (Mains) 2009, U.P. U.D.A./L.D.A. (Pre) 2001 |
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| Isotopes of Hydrogen | Protium (H1) has no neutron; Deuterium (H2) has one neutron; Tritium (H3) has two neutrons. |
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| Isobars | Atoms of different elements (different protons) having the same mass number (A). |
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| Isoelectronic | Ions and atoms with an equal number of electrons, thus having the same electronic configuration. Neon (Ne), Sodium ion (Na⁺), Magnesium ion (Mg²⁺), and Fluoride ion (F⁻) all have 10 electrons and thus are isoelectronic species |
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| Beta Particles |
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| Negatively charged, highly energetic electrons released from the nucleus. Deflected towards the positive charged plate. |
| Gamma Rays | Neutral electromagnetic radiations (photons). Not deflected in electric and magnetic fields. |
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| Fundamental Particle | A particle with no sub-structure. Among the choices of neutron, proton, pi-meson, and quark, Quark is a fundamental particle. | U.P. R.O./A.R.O. (Mains) 2017 |
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| Higgs Boson | Often known as the "God Particle". Its existence helps explain why elementary particles possess mass. |
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| Filling of Orbitals | Governed by Aufbau's principle, which states that electrons fill orbitals starting at the lowest available energy levels. |
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