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# Bohr Rutherford Diagram and Introduction

### Key Concepts

• Atom

• Shell

• Attractive force

• Repulsive force

## Introduction

Atoms are the basic unit of every object. They are composed of three main things called electrons, protons and neutrons. The protons and neutrons together are called a nucleus, and the electrons revolve around the nucleus in a circular orbit. The complete structure is called an atom. We know that opposite charges attract each other, protons are the positively charged particles, and the electrons are negatively charged particles. This says that electrons and protons attract each other.

The attractive forces between the electrons and the protons in the atom are balanced by the repulsive force between the electrons. The electrons in the atom are situated in a particular manner that the electrons are mostly balanced. The electrons are arranged around the nucleus in a circular orbit. The number of orbits is not fixed for every atom. It depends on the number of electrons present in the atom.

To maintain the perfect balance between the attractive and repulsive force in the atom, there must be a specific number of electrons in each orbit. Niels Bohr and Ernest Rutherford studied it and found the number of electrons each orbit needed to maintain the balance between the forces. They drew a diagram to represent the electrons in each orbit.

Each orbit in the atom is called an energy shell or energy level. The shell nearest to the nucleus can hold a maximum of 2 electrons. So the first two electrons of the atom are in the first shell of the atom. Once the first shell of the atom is filled, it cannot hold more electrons and the electrons move to the second shell of the atom. The second shell of the atom can hold a maximum of 8 electrons. The electrons from three are taken to the second shell until it is completely filled. By the end of the fill of the second shell with electrons, the atom would have completely held 10 electrons in total. The first two are in the first shell and 8 in the second shell. Similarly, the third shell can hold a maximum of 18 electrons. The fourth shell can hold a maximum of 32 electrons.

In this manner, the allotment of the number of electrons in each shell is given,  and the representation of it in a diagrammatic manner is given as well. The count of the s orbit or the shell is taken with a notation of small n. The value of the n is always a natural number. It starts from 1 and takes only numbers.

As the number of shells increases, the attractive forces between the nucleus and the last shell of the atom decrease. The electrons in the first shell are tightly bonded with the nucleus. As the shell number increases, the attractive force decreases.

The Bohr-Rutherford diagram contains a circle at the center representing the nucleus of the atom. The circle contains the chemical symbol, number of protons, number of neutrons present in the atom. The circular arcs are drawn around the circle representing the shells of the atoms for the electrons. As per the shell capacity of holding the electrons, the electrons are placed.

Let us take the element oxygen. The oxygen has the chemical symbol O, which contains 8 electrons, 8 protons, 8 neutrons. The atomic mass of the oxygen is nearly 16. Of the 8 electrons, the oxygen contains the two are placed in the first shell of the atom. So we place the two dots in the first shell representing the electrons. The rest of the electron count is 6. So we see the capacity of the second shell, and we clearly see that the remaining electrons are less than the capacity of the shell. So the remaining electrons are in the second shell itself. So we place the 6 dots in the second shell. Here there is no need for the third and fourth, and higher shells for the atom.

### Summary

• Atom is the basic unit containing electrons, protons, and neutrons.

• Electrons are arranged around the nucleus in circular orbits.

• Each orbit can contain some specific number of electrons.

• Neil Bohr and Ernest Rutherford had studied the arrangement and gave the diagrammatic representation for it.

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