Explain Bohr's model of an atom.
Answers
Neils Bohr gave atomic model in 1913.The main points of this model are:
1) An atom consists of a central positive part called the nucleus which contains all the protons and neutrons.
2) Electrons which are present outside the nucleus revolve around the nucleus in definite circular paths called orbits or shells.
3) Each orbit has a fixed energy and the orbitals are represented by the symbols K, L,M, N etc or by the numbers 1,2,3 …
4) Each orbit can accommodate not more than a fixed number of electrons.
5) Electrons moving in the same orbit donot lose or gain energy.
6) Electrons lose energy on jumping from a higher orbit to lower one and vice-versa.
Answer:
Step-by-step explanation:
A Danish physicist named Neil Bohr in 1913 proposed the Bohr atomic model. He modified the problems and limitations associated with Rutherford’s model of an atom. Earlier in Rutherford Model, Rutherford explained in an atom a nucleus is positively charged and is surrounded by electrons (negatively charged particles).
The electrons move around in a predictable path called orbits. Bohr modified Rutherford’s model where he explained that electrons move around in fixed orbital shells. Furthermore, he explained that each orbital shell has fixed energy levels. Therefore, Rutherford basically explained a nucleus of an atom whereas Bohr took the model one step ahead. He explained about electrons and the different energy levels associated with it.
According to Bohr Atomic model, a small positively charged nucleus is surrounded by revolving negatively charged electrons in fixed orbits. He concluded that electron will have more energy if it is located away from the nucleus whereas the electrons will have less energy if it located near the nucleus.
Bohr atomic model
Bohr’s Model of an Atom
Postulates of the Bohr Atomic Model
Electrons revolve around the nucleus in a fixed circular path termed “orbits” or “shells” or “energy level.”
The orbits are termed as “stationary orbit.”
Every circular orbit will have a certain amount of fixed energy and these circular orbits were termed orbital shells. The electrons will not radiate energy as long as they continue to revolve around the nucleus in the fixed orbital shells.
The different energy levels are denoted by integers such as n=1 or n=2 or n=3 and so on. These are called as quantum numbers. The range of quantum number may vary and begin from the lowest energy level (nucleus side n=1) to highest energy level. Learn the concept of an Atomic number here.
The different energy levels or orbits are represented in two ways such as 1, 2, 3, 4… or K, L, M, N….. shells. The lowest energy level of the electron is called the ground state. Learn the concept of Valency here in detail.
The change in energy occurs when the electrons jump from one energy level to other. In an atom, the electrons move from lower to higher energy level by acquiring the required energy. However, when an electron loses energy it moves from higher to lower energy level.
Therefore,
1st orbit (energy level) is represented as K shell and it can hold up to 2 electrons.
2nd orbit (energy level) is represented as L shell and it can hold up to 8 electrons.
3rd orbit (energy level) is represented as M shell and it can contain up to 18 electrons.
4th orbit (energy level) is represented as N Shell and it can contain maximum 32 electrons.