Category: Ch 4 – Structure Of The Atom

Isotopes are defined as the atoms of the same element, having the same atomic number ( number of protons ) but different mass numbers ( number of protons+neutrons ).For example: In the case of Hydrogen we have:Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars.For example,…

Orbits are energy shells surrounding the nucleus in which electrons revolve. Electron distribution in different orbits The distribution was suggested by Bohr and Bury; The maximum number of electrons present in a shell is given by the formula 2n2, where ‘n’ is the orbit number or energy level index, 1,2,3,…. The maximum number of electrons…

Properties of electrons, protons and neutrons Bohr’s Model of an atom Bohr came up with these postulates to overcome the objections raised against Rutherford’s model: Electrons revolve around the nucleus in stable orbits without emission of radiant energy. Each orbit has a definite energy and is called an energy shell or energy level. An orbit…

Rutherford concluded the model of the atom from the α-particle scattering experiment as: (i) There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus. (ii) The electrons revolve around the nucleus in well-defined orbits. (iii) The size of the nucleus is very…

Rutherford’s experiment and observations In this experiment, fast-moving alpha (α)-particles were made to fall on a thin gold foil. His observations were: A major fraction of the α-particles bombarded towards the gold sheet passed through it without any deflection, and hence most of the space in an atom is empty. Some of the α-particles were deflected…

Radioactivity Radioactivity is the term for the process by which an unstable nucleus of an atom loses energy by giving out particles. It does so by giving out particles such as alpha and beta particles. This process is spontaneous. An atom is unstable if the nucleus has an imbalance, meaning a difference in the protons…

Electrons are the negatively charged sub-atomic particles of an atom. The mass of an electron is considered to be negligible, and its charge is -1. The symbol for an electron is e– Electrons are extremely small. They are found outside the nucleus. Thomson’s model of an atom According to Thomson,(i) An atom consists of a positively…

Atoms Atoms are the building blocks of matter. It is the smallest unit of matter that is composed of three sub-atomic particles: the proton, the neutron and the electron. Cathode ray experiment J. J. Thomson discovered the existence of electrons. He did this using a cathode ray tube, which is a vacuum-sealed tube with a cathode and anode on…

Essentially, the structure of an atom comprises protons, neutrons and electrons. These basic components provide the mass and charge of the atoms. The nucleus comprises proton and neutron, with the electron orbiting around that.