SUB-ATOMIC PARTICLES
Before studying about subatomic particle
we should know in brief what is atom?
Atom-: Atom is the smallest particle of any element.
In the old time, It is assumed that atom is indivisible but with the help of new discoveries , this assumption thauut atom is indivisible is failed. Now all know that atom is divisible and it is formed of more small particles called subatomic particles.
Atom is divisible further ,this can be considered with the study of static electricity and conduction of electricity in the conductor.
Events which shows atom is divisible-
- Flowing of electricity in Conductor.
- Transfer of heat from one point to another.
- Attraction or Repulsion b/w charged species.
Sub-atomic Particles-There are three classical sub-atomic particles. These are as follows...
1- Electron
2-Proton
3-Neutron
It belongs to the Lepton Family in which Electron is kept. It is sub-atomic Indivisible Particle.It was discovered by J.J.Thomson. It possesses negative charge as 1.6×10¯l9. Mass of an electron as 9.1×10¯З।. It can be represented by e¯ or β¯.
Properties of electron-
1-Electrons revolve around the nucleus in the definite energy levels
2-Electron shows Circular and Spin motion.
Note-Circular motion is the motion in which one body rotates around another body in a circle while Spin motion is the motion in which body rotates on its own axis.
3-Electron shows spin quantum no.that is as +1/2 or -1/2.
If atom spins in clockwise direction then Spin Quantum no. will be written as +1/2.
If atom spins in anticlockwisedirection then Spin Quantum no. will be written as -1/2.
4-Electron shows wave nature as well as particle nature.
5- Electron radiate energy or absorb....
If it radiates energy it means it is going to lower energy level from higher energy level of an atom.
If it absorbs energy it means it is going to higher energy level from lower energy level an atom.
Electron is going from higher energy level (n=2 ) l to lower energy level(n=1) by emitting photon
In the similar way it can go from low energy level to high energy level by absorbing photon
Note-Electron can absorb or radiate energy in the form of Photon.
6-Atom has provided neutrality to the atom.
Note- No. of electrons are just equal to the no. of protons in the nucleus in an atom.
7-Positive or Negative charge to an atom is due to the lack or excess of electrons in this state this charged atom is called ion. eg Na+, Cl‾
8-The mass of proton to mass of electron ratio is 1836..i
mass of proton/mass of electron=1836/1
=1836
9-if shows repulsion to negatively charged species while attraction to positively
charged species.
10-Electrons are bound by electromagnetic force to atomic nuclei. The knowledge of their orbital shape, orbits , spin and electromagnetic effects are denoted by the quantum nos.
Role of Electron in Chemistry
1-Electrons are responsible to provide the valency to an atom eg. Na contain only one electron in outermost shell so valency is one (+1)and Cl is short by one electron to complete its octet ,so its valency also one (-1)
The atom whose outermost shell is complete
means has eight electrons (octet) in
outermost shell only helium is satisfied with 2 electron in outermost shell it contain only one shell, then its valency is 0. eg in He, Ar and Kr.
If any atom such as carbon contains 4 electron in outermost shell it means its valency is 4.
Note-Valency of Carbon is in intermediate form. So it has a power to be combined to most of elements. Catanation power is that in which atom of an element has a capacity to be combined to itself. The catanation power of carbon is highest. This is why that most of the compounds in the nature are as hydrocarbons.
Valency=n ( if no. of electrons in outermost shell is equal or lesser than 4) like in B (atomic no.)is 5 =2,3 so n=3 so valency is 3
valency=8-n where n=no of electrons in outermost shell.
above formula applied only when no. of electron in outermost shell is equal to or more than 4. n= 4 or n>4 and in this case valency will be negative eg. Nitrogen 7=2,5 then valency= 8-n=8-5=3. since nitrogen is non-metal so valency is -3.There are more valencies of nitrogen but general valency is -3. Other valencies of nitrogen depends on the elements to those it is combined.
2- All the reactions are based on the transferring of the ions but ions are formed by the transferring of electrons.All chemical reactions are due to the electrons.
3-Electrons are responsible for conduction of electricity.
4-Electron plays essential role in numerous Physical Phenomenon such as Electricity ,Magnetism, Thermal conductivity and Resistivity etc.
5- Electron plays important role in construction of an atom and providing neutrality to the atom.
6- With the help of electron we can elucidate how electrophile (positively charged ion or species which attract electron ) nucleophile ( negatively charged species which attract positively charged ion) are formed.
difference b/w subatomic and fundamental particles.
Classical Subatomic Particles are electron Proton and neutron but remember that proton and neutron are not fundamental particles ,while electron is subatomic and fundamental particle both. Electron is single and do not consist of other smaller particles.
Fundamental Particles are the particles which do not consist of other particles. Other particle do not take part in formation of that particle. Electron is such type particle. On the other hand proton and neutron both consist of other smaller particles called quarks.
Leptons-
Lepton includes six fundamental particles
Electron
Muon
Tau
Electron Neutrino
Muon Neutrino
Tau Neutrino
We have told u earlier about electron.
Muon is similar to electron but heavier to it too. when high energy particles collide in an atomic generator ,this muon is produced.
Tau is similar to Muon but heavier to it. both Muon and Tau are unstable and exist in nature for a very short time.
Proton- Protons are the subatomic particle not fundamental. Protons are found in the nucleus. The charge on proton is +1 . It is just positive and equal to +1.6×10￣19 C. Mass of the proton is 1.67×10‾27kg.
The quark content of a proton -
The colour assignment of individual quark is arbitrary , but all three colour must be present. Forces b/w quarks are mediated by gluon.
The charge on up quark- +2/3 e
The charge on down quark -1/3
Classification = Bryon
Composition 2 up quarks
1 down quark
statistic fermionic
interaction gravity
electromagnetic
weak , strong
symbol P, P+, H+
theorised by William Prout
discovered observed as H+ by Eugen Gold stein
mass 1.67×10¯27 kg.
mean life time 2.1×10२9 years
(stable)
charge + e
radius .87 Fm
spin 1/2
polarity +1
magnetic polarisability1.9×10¯4Fm3
magnetic moment 1.4×10¯ 26 JT¯1
Neutron-Neutron was discovered by James Chadwick and Theorised by Ernest Rutherford. The neutron is a sub-atomic Particle. Its symbol is n or n° with no net charge ( 0 e ) and mass is slightly more than that of mass of Proton (mass of n=1.6749×10¯27 kg. Neutron is called nucleon like Proton.
Classification,composition, statistics and interaction are same that of Proton. Mean life is 881.5 s. Spin and isospin is +1/2 and -1/2 respectively. Electric Polarizability and electric dipole are 1.16×10¯3 fm3 and 2.9×10¯26e.cm respectively.
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