Atom and the Nucleus, nucleur fission and nuclear reactor process, for GSEB std 8 to 12 Science.

Neuclear reactor process.

Atom and the Nucleus.

Atom :- The smallest part of an element that can exist. It consists of a nucleus of protons and neutrons, surrounded by orbiting electrons.

Atom diagram

Moving process of Atom

Every single thing you can see, hear, feel, smell, and taste is made from microscopic particles. These particles are called atoms, and it would take millions of them just to cover a full-stop. An atom is itself made up of even smaller particles. In the center of each atom there is a nucleus made up of protons and neutrons. Particles called electrons whiz around this nucleus in different shell(layers). Protons and neutrons are much heavier than the electrons, so the nucleus makes up most of an atom’s mass. Some substances, such as water, are made up of molecules. These consist of several kinds of atoms joined together in a group. Other substances, such as iron, have just one kind of atom. 

Protons, Neutrons, & Electrons.

Proton, Neutron and Electron

The nucleus of every atom contains two types of particle protons and neutrons. The number of protons gives the atomic number. Protons have a positive electric charge, while neutrons have none. The electrons that spin around the nucleus, like planets orbiting the sun, have a negative charge. But electrons are not solid balls, they are bundles of energy that move almost as fast as light. There are always the same number of electrons and protons in an atom.

Nucleus.

Nucleus

A nucleus is made up of two types of particles, neutrons which do not carry any charge; and protons which carry a positive charge exactly equal in magnitude to that of an electron; i.e. 1.6 * 10^-19  coulomb. Protons and neutrons have similar masses, but neutron is slightly heavier; both of them being much more massive than electrons. Neutron is 1838.65 times more massive than an electron, proton is 1836.12 times more than electron. The simplest nucleus is that of an atom of ordinary  hydrogen and consists of only a single proton. Both protons and neutrons are commonly known as nucleons.

The Schrodinger Model :-  abandoned the idea of precise orbits, replacing them with a description of the regions of space ( called orbitals) where the electrons were most likely to be found.

Orbitals:- electrons with various values of angular momentum occupy regions of space like these. Shading sows probability of finding an electron at that distance.

The Bohr Model :- ‘quantized’ the orbits in order to explain the stability of the atom.

Bohr's Model

The Rutherford Model :- pictured the atom as a miniature solar system with the electrons moving like planets around the nucleus.

The Rutherford Model

Scattering experiment by Rutherford.

Models of the Atom

Experimental data have been the impetus behind the creation and dismissal of physical models of the atom. Rutherford’s model, in which electrons move around a tightly packed, positively charged nucleus, successfully explained the results of scattering experiments, but was unable to explain discrete atomic emission—that is, why atoms emit only certain wavelengths of light. Bohr began with Rutherford’s model, but then postulated further that electrons can move only in certain quantized orbits; this model was able to explain certain qualities of discrete emission for hydrogen, but failed for other elements. Schrödinger’s model, in which an electron is described not in terms of definite paths but in terms of the likelihood of finding the electron in a particular region, can explain certain qualities of emission spectra for all elements; however, further refinements of the model, made throughout the 20th century, have been needed to explain further spectral phenomena.

Nucleur  fission process.

Nucleur  fission process

Nucleur  fission process

When a nucleus is bombarded with a neutron, it absorbs the neutron and then breaks up into two roughly equal nuclei. This process is called the nuclear fission.

Nuclear Reactor activity.

A nuclear reactor works on the principle of steadily sustained nuclear chain reaction. It uses fissile nuclei like ₉₂u²³⁵  and Pu²³⁹ . Use  of appropriate moderator coolant and control rods are essential to the proper design of a reactor using some specific fissile material as fuel gives the scheme to a reactor using slow neutrons. The coolant flowing in through  X carries away the energy generated in the form of heat through Y.

Fission and Fusion Processes.

Fission and Fusion Processes

Nuclear energy can be released in two different ways: by fission (splitting) of a heavy nucleus, or by fusion (combining) of two light nuclei. In both cases energy is released because the products have a higher binding energy than the reactants. Fusion reactions are difficult to maintain because the nuclei repel each other, but, unlike fission reactions, fusion reactions create far less radioactivity.