What is Atom, Definition, History, Types, Structure & Parts

Hello, fellows, I hope all of you are having fun in your life. In today’s tutorial, we will discuss what an atom is. Every type of matter is created with different types of atoms, and atoms also consist of three main components: the first one is a neutron, the second one is a proton, and the third one is an electron. Electrons in an atom revolve around the nucleus, and protons and neutrons are located in the center of the nucleus. In the periodic table, every element has a specific atom structure; in an element, all atoms have the same value for the proton numbers.

At the time of the invention of an atom, it was considered that an atom is a single particle and no further particles exit in it. But with the passage of time, it was found that an atom is not a single particle, but it also comprises some subparts in its composition. In its center, there is a nucleus around which electrons are moving, as in solar system planets are moving in a circular path. In today’s post, we will have a look at the atom’s structure, particles, and some related theories to an atom. So let’s get started with what an atom is.

What is Atom

Bohr Model

• The atom is the least particle of any element that has the ability to take part in chemical reactions like elements.

• The atom of any element has the same properties and features shown by the element.

• Almost there are one hundred and eight elements that have been discovered that consist of different numbers of atoms. All atoms of these elements are different from an atom of other elements.

• Due to the different features and structures of an atom, every element shows different behavior from other elements.

• The famous physicist Neil Bohr, who was famous physicists explains the structure that it is similar to our planet system in which all planets are revolving around the sun similarly in atoms, and all electrons are rotating around the nucleus.

• The nucleus of an atom comprises the two particles. The first one is the proton that has a positive charge, and the second one is the neutron that has zero charges.

• In every atom, there is a specific number of protons and electrons that are not similar to other atoms of different elements.
• In the figure given below, you can see two different atoms: the first one is hydrogen and the second one is helium.
• You can see that hydrogen has one proton and one electron, while helium has 2 protons (P) and 2 neutrons (N).

• Atomic numbers of all the elements are shown on the periodic table.

Atomic Number

• If we observe that all elements in the periodic table are placed in groups and periods of a table according to their atomic numbers.

• The number of protons in the nucleus of an atom defines the proton number of an atom.

• It is also equal to the number of electrons in such atoms that have the same number of electrons and protons, such as an atom of hydrogen.

• Similarly, in the atom of helium, the atomic number is 2, which is equal to the number of protons and electrons in the atom.

Electrons and Shells

Energy Levels

• The electrons of an atom revolve in specific orbits at a specific distance around the atom according to energy.

• The energy of electrons near the nucleus of an atom is less than the energy of electrons that are away from the center of an atom.

• In atoms, there are different levels of energy, so electrons revolve at different energy levels.

• Every orbit of an atom has a specific value of energy. In an atom, the orbits are grouped into energy levels called shells.

• Every atom has a specified value of shells, and every shell has a certain number of electrons. These shells start from one and continue till the last number according to the atom and the number of electrons in an atom.

• In the given figure, you can see the atomic structure of silicon that has fourteen electrons and fourteen protons and neutrons in the nucleus.

How to find the maximum number of electrons in a shell?

• The number of electrons in any shell can be denoted as Ne can be found by using this given formula.

N_e =2n²

• In this formula, ‘n’ represents the number of shells of an atom. If we find the number of atoms in first shell, then we will have.

N_e =2(1)²  = 2

• The number of electrons in the second shell will be.

N_e =2(2)²

=2×4=8

• The numbers of electrons in the third shell will be.

N_e =2(3)²

=2×9=18

• The number of electrons in the fourth shell will be.

N_e =2(4)²

=2×16=32

What are valence electrons?

• The electrons in an atom revolving in the last shell of an atom are called valence electrons.

• The energy of these electrons is larger as compared to other or less distant electrons from the nucleus.

• Due to the larger distance, the force of attraction of the nucleus on these electrons is also weaker.

• The last shell of an atom that has valence electrons is called the valence shell.

• The valence electrons take part in different chemical reactions and define the properties of the atom.

• Every electron in any shell requires a specific value of energy to leave their respective shell when valence electrons get the respective energy, they leave the shell, and this ability explains the conductivity behavior of any material.

What is ionization?

• When the required energy of electrons in an atomic shell is provided either from any heating element or from the light, they will leave their respective shells.

• The required energy depends on the distance from the nucleus; if an electron is close to the nucleus, it will require a large amount of energy due to a large force of attraction between the nucleus and the electron.

• If an electron is in a valence shell, it will need a smaller amount of energy to leave the shell.

• The energy required for the electron to leave the shell is known as ionization energy.

• When an electron leaves the atom at the place of the positive ion, the number of protons in the atom increases.

• The complete process of elimination of electrons from the atom is called ionization.

• For instance, as we know, the symbol of a hydrogen atom is H. When the outermost shell electron or valence shell electron leaves the atom, a positive ion will be created that is denoted as H+. The eliminated electron from the atom is known as the free electron.

• If, instead of eliminating an electron from an atom, it adds to the atom, this process creates a negative ion and also releases energy from the atom.

• The removal or addition process of an electron does not happen in only a single atom in different reactions; more than one atom releases or gets electrons according to reaction requirements.

Quantum Model of Atom

• Normally the atomic model given by Bohr is widely used due to easy understanding, but it does not provide some detailed explanation.

• Instead of the Bohr model, the quantum model of an atom is think to detailed and correct atomic model.

• The quantum atomic model is a little bit complicated to understand as compared to the Bohr model.

•  For an understanding of a quantum model, two theories explain the quantum model in detail.

• Wave-particle duality.

• Uncertainty principle.

• Now we discuss these two in detail.

Wave-Particle Duality

• This theory about electrons says that, like light, electrons also show two behaviors of waves and particle-like.

• The speed with which the electron is moving in its respective orbit represents its wavelength that interacts with the adjacent electron’s wave and adds up or cancels them at different points.

Uncertainty Principle

• As we are familiar with the behavior of a waveform that continuously changes its behavior, according to the uncertainty principle, the position of an electron can not be specified.

• The uncertainty principle was given by Heisenberg, who says that it is very difficult to find the speed with which an atom is moving and position at the same time with accuracy.

• As we discussed above, the quantum model is complex as compared to the Bohr model in the sense that in the quantum model, every shell also has further shells or subshells that are known as energy levels.

• These subshells are denoted as s, p, d, and f. In an s subshell, only 2 electrons can reside.

• P has 6 electrons, d has 10, and f has 14 electrons.

• Every atom can be explained with the atom arrangements that have shells and subshells and electrons in these subshells according to their position.

•  For instance, in a given table you can see the nitrogen configuration and electron distribution in shells.

•  The structure of orbitals or subshells is not like the shells explained in the Bohr model.   In the quantum model, every shell in the Bohr model is a 3-dimensional space covering the atom that denotes the average value of the energy of the electronic cloud.

• The electronic cloud term is used for the area around the electrons that shows the electron’s existence.

• In a 3-D representation of a quantum model of an atom’s S subshell or orbitals, the shape is similar to the sphere.

• For the first energy level, the structure of the sphere is solid, while in higher energy levels, every s subshell consists of spherical shapes, which are nested shells.

• The structure of the p subshell in the second shell has 2 elliptical-shaped lobes that also have a tangent point on the nucleus.

• The 3 p subshells in every shell are located at 90° to each other. One p subshell at the x-axis, a second at the y-axis, and a third at the z-axis.

• For instance, the quantum model of a sodium atom consists of eleven electrons and is drawn in the given figure below.

Difference between Atoms and Moles

• Now we compare atoms and moles and find their differences.

Differences between Atoms and Molecules

• Now we discuss the difference between atom and molecules.

Read also

• Difference Between Atom vs Molecule
• What is Semiconductor? Working, Types, Features, & Uses

That is the detailed post on atom I have mentioned each and every parameter related to an atom. If you have any questions about this tutorial ask in comments. See you in the next tutorial.