High School Physics


Isotope worked example

Three stable isotopes of oxygen are Give the number of (i) protons, (ii) nucleons, and (iii) neutrons in each isotope. Answer: Oxygen-16i number of protons Z = 8ii number of nucleons A =16iii number of neutrons = A – Z = 8Oxygen-17i number of protons Z = 8ii number of nucleons A =17iii number of […]

What are the characteristics of alpha, beta, and gamma radiation?

Radiation is a term that describes all the ways energy is emitted by the atom as X rays, gamma rays, neutrons, or charged particles. Most atoms, being stable, are nonradioactive; others are unstable and give off either particles or gamma radiation. Substances bombarded by radioactive particles can become radioactive and yield alpha particles, beta particles, […]

Aufbau Principle – how an electron enters subshell

Aufbau Principle: An electron enters the sub­shell that has the least energy. The subshells are filled in the increasing order of energy. The ascending order is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d,…. Order of filling the subshells: 1s < 2s < 2p < […]

Electronic configuration & quantum numbers

Electronic configuration: The distribution of electrons in an atom is known as electronic configuration. Spectroscopic studies, which are used in elucidating electronic configuration show that four numbers known as quantum numbers are required to characterize each electron in an atom. Principal Quantum number (n) Principal Quantum number (n): It represents the main electronic energy shells […]

Atomic Structure – shell model, based on the Bohr model

In this post, various aspects of the shell model of the atomic structure (based on the Bohr model) have been discussed. Electron Orbits There are as many orbiting electrons as there are protons in the nucleus. The radii of the electron orbits are assumed to be quite larger than the size of the nucleus. In […]

Important formulas related to Atomic Structure

In this post, you will find a bunch of important formulas related to atomic structure. formulas related to atomic number & mass number (a) Atomic number (Z) = number of electrons = number of protons (b) Mass number (A) = number of protons + number of neutrons = atomic number + number of neutrons (c) […]

The atoms of the first 20 elements in the periodic table

In the Periodic Table, the elements are arranged in order of increasing proton number. Here is a quick list of the names of the first 20 elements in the periodic table: hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, magnesium, aluminium, silicon, phosphorus, sulphur, chlorine, argon, potassium, & calcium. In this post, […]


Isotopes are atoms of the same element, with different numbers of neutrons. The nuclei of different isotopes of the same element have the same number of protons but different numbers of neutrons. Most elements have isotopes. For example, calcium has six, magnesium has three, hydrogen has three, iron has four, and chlorine has two isotopes. […]

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