Atom is the smallest particle of the matter.
According to the Dalton, atom (Greek word “atomos” means indivisible).
The smallest part of an element that can enter into a chemical combination and can’t exist in free state.
It is the building block of matter.


Atom Sub-atomic Particles:
More than hundred sub-atomic particles like electrons, protons, positrons, antiprotons, mesons, quarks, neutrino and antineutrino etc have been discovered in an atom.

However, electrons, protons and neutrons are the fundamental sub-atomic particles of atoms as they are all present in all types of atoms except the one that is protium (1H1).
Protium (1H1) contain s one electron , one proton and no neutron.
Electrons revolves around the nucleus of an atom.
Protons and Neutrons are present inside the nucleus of an atom.
Charge on Sub-atomic Particles:
Electrons
Protons
Neutrons

Watch Now !!!
Structure of an atom| Carbon & Oxygen atom | Atomic Number and Mass Number | Ion- Cation vs Anion
If you want to know about shells ,subshells and orbitals,so just Click the below post link:
Difference Between Shells , subshells and Orbitals

ORBIT / SHELL:
An orbit is a well-defined circular path in which electron revolves around the nucleus of an atom.
An orbit is also called as Energy level/ shell.
Orbit / shell are as follow:
K shell (max 2 electrons)
L shell (max 8 electrons)
M shell (max 18 electrons)
N shell (max 32 electrons)
And so on…..
MAXIMUM NUMBER OF ELECTRON CALCULATION:
FORMULA:
MAX. NO OF ELECTRON IN A SHELL= 2n 2
SUB ORBITS
A sub-orbit is a sub division of electron shells(orbit) separated by electron orbitals.
Sub orbit also known as sub shells or sub energy level.
Sub shells are denoted by:
(s)sharp (p) principle (d) diffuse (f) fundamental
ORBITALS:
It is a three dimensional probability space around the nucleus of an atom where the possibility of finding the electron cloud is maximum (95%).

TYPES OF ORBITALS:
s orbital
p orbital ( px ,py , pz )
d orbital (dxy, dyz, dzx, dz2 , dx2-y2 )
f orbital (7 in number with complex structure)

Also Watch !!!
Difference between Shell , Sub-shell and Orbitals ( in Urdu / Hindi )
Isotopes: Definition, Types and Examples Animation

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What is an isotope- Definition,Types and Examples
Do you Know!!!
Octet Rule and Duplet Rule:
Octet Rule:
The tendency of an atom to acquire 8 electrons in outermost shell in order to attain the noble gas configuration and becomes stable.
Duplet Rule:
The tendency of an atom to acquire 2 electrons in outermost shell .
Atoms with low atomic number such as hydrogen and helium followed the duplet rule
What is the difference between Octet Rule and Duplet Rule
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