Structure of An Atom

Structure of an atom

Structure of an atom:

We know that the most fundamental unit of matter which is capable of independent existence is the atom.

 

The above figure shows the structure of an atom.

An atom consist of a nucleus at the center and there are tiny particles moving around it called electrons. These electrons are negative charge particles. The nucleus of an atom consists of two types of particles called protons and neutrons (except hydrogen atom, the nucleus contains only one particle and that is proton).

These two particles (protons and neutrons) have almost the same mass. Proton is a positively charged particle and neutron is electrically neutral, means there is no charge on the neutron. All the mass of an atom is concentrated in its nucleus.

The electrons revolving around the nucleus are very light. An electron is about 1850 times lighter than a proton or neutron. An electron has the same amount of charge as a proton, but they are negative charged.

Since matter in its normal state is electrically neutral. Because there are same number of electron and proton present in the atom.

There are no difference between an electron in an atom of copper and an electron in an atom of aluminum or any other element. Similarly, there is no difference between a proton in one atom and a proton in another atom of a different element. And also the neutrons in the atoms of various elements are identical.

 

So we say that the electrons, protons, and neutrons are the fundamental particles of the universe.

 

Now questions is arrived that why various elements behaves differently?

 

This is because of the difference in the number and arrangement of the electrons, protons, and neutrons of which each atom is composed.

 

The number of protons or electrons in an atom is called the atomic number of an atom.

 

All the electrons of an atom do not move in the same orbit.

The electrons arranged in different orbits or shells. The first orbit can hold a maximum of two electrons. The second orbit can hold a maximum of eight electrons.

The third one holds maximum eighteen (18) electrons,

The fourth not more than 32 electrons and so on.

 

In general, a shell can contain a maximum of 2n2 electrons, where n is the number of the shell.

But there is an exception to this rule, the outermost orbit in an atom cannot hold more than eight (8) electrons. The electrons present in the outermost orbit are called valence electrons.