Showing posts with label atom. Show all posts
Showing posts with label atom. Show all posts

Monday, 30 July 2012

Elements from the Periodic Table which do not exhibit Magnetism.


NO MAGNETISM

a) For a material to be magnetic, it must have electron spin.

b) Electron spin gives the substance an Electronic Angular Momentum to interact with the magnetic field.

c) Thus if the electrons in an atom spins in the same direction,the atom will produce a magnetic field and will respond to the forces of a magnet.

d) But in most atoms,electrons occur in pairs and these paired electrons spin in opposite directions.

e) These opposite spins of electrons causes their magnetic fields to cancel each other, such that no net magnetic field is produced and this could be the reason why some elements do not exhibit magnetism.

f) However at a low temperature a substance may have one kind of magnetic properties whereas at a higher temperature it may have another type of magnetic behavior.

g) Thus the conclusion is that Magnetic Properties of a substance is a very complicated topic, and it is very difficult to assign some materials as being strictly magnetic and others to be strictly non-magnetic.

Elements from the Periodic Table which do not exhibit any type of Magnetism are :-

1) Fluorine
2) Potassium
3) Scandium
4) Vanadium
5) Rubidium
6) Yttrium
7) Niobium
8) Technetium
9) Iodine
10) Cesium
11) Lanthanum
12) Praseodymium
13) Promethium
14) Ytterbium
15) Lutetium
16) Hafnium
17) Tantalum
18) Rhenium
19) Polonium
20) Astatine
21) Radon
22) Francium
23) Radium
24) Actinium
25) Thorium
26) Protactinium
27) Uranium
28) Neptunium
29) Plutonium
30) Americium
31) Curium
32) Berkelium
33) Californium
34) Einsteinium
35) Fermium
36) Mendelevium
37) Nobelium
38) Lawrencium
39) Rutherfordium
40) Dubnium
41) Seaborgium
42) Bohrium
43) Hassium
44) Meitnerium
45) Darmstadtium
46) Roentgenium
47) Ununbium
48) Ununtrium
49) Ununquadium
50) Ununpentium
51) Ununhexium
52) Ununseptium
53) Ununoctium

Sunday, 29 July 2012

What is Ferromagnetism ? Behaviour of Ferromagnetic Substances & the Elements which exhibit Ferromagnetism..!


FERROMAGNETISM

a) The term Ferromagnetism was coined by Curie Pierre in 1895 .

b) Those substances which when placed in a magnetic field, are strongly magnetised in the direction of the applied field are called as Ferromagnetic substances.

c) A Ferromagnetic substance when placed in a non-uniform magnetic field, show a very strong tendency to move from the weaker to the stronger parts of the magnetic field.

d) Ferromagnetic materials are made up of atoms with permanent dipole moments.

e) Ferromagnetic substances retain their magnetism even when the external magnetic field is removed. This tendency of Ferromagnetic substances to remember their magnetic history is called as " Hysteresis " .

f) Due to their this property Ferromagnetic substances can be converted into Permanant Magnets.

g) Being Permanant magnets the Ferromagnetic substances can give rise to a magnetic field even in the absence of an external magnetic field.

h) Ferromagnetic substances have very high Magnetic Susceptibilities, ranging from 1000 to 1,00,000 .

i) The Relative Permeability of the Ferromagnetic substances is much more greater than 1 and hence for a Ferromagnetic substance the magnetic lines of force are strongly attracted.

j) When a Ferromagnetic substance is heated above a certain temperature it loses it's ferromagnetism and become Paramagnetic.

k) The temperature at which a Ferromagnetic substance becomes Paramagnetic is called as Curie Temperature.

l) Ferromagnetism is exhibited by solid materials only.

Elements from the Periodic Table which exhibit Ferromagnetism are :-
1) Iron
2) Cobalt
3) Nickel
4) Gadolinium

Anti-Ferromagnetism

a) Antiferromagnetism was first discovered by Neel and Bitter and later extended by Van Vleck.

b) In the presence of a strong magnetic field, Antiferromagnetic materials are weakly magnetised in the direction of the applied field.

c) In Antiferromagnetic materials, the magnetic moments are aligned in opposite directions and are equal in magnitude.

d) Due to this the magnetic moments of the neighbouring atoms cancel each other and its net magnetisation is zero.

e) Antiferromagnetism occur commonly among transition metal compounds, especially oxides.

f) Antiferromagnetism generaly exist at low temperatures and vanishes at and above a certain temperature called the Neel temperature .

g) Above the Neel temperature, the Antiferromagnetic material is typically paramagnetic .

h) Chromium is an example of element which exhibit Antiferromagnetism.

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What is Paramagnetism ? Behaviour of Paramagnetic Substances & the Elements which exhibit Paramagnetism..!


PARAMAGNETISM

a) The term Paramagnetism was coined by Curie Pierre in 1895.

b) Those substances which when placed in a magnetic field are weakly magnetized in the direction of the applied field are called as Paramagnetic Substances .

c) A Paramagnetic Substance when placed in a non-uniform magnetic field, begins to move form the weaker region to the stronger region of the magnetic field.

d) Thus the magnetic field lines prefer to pass through the Paramagnetic substances and this is the reason why the Paramagnetic Substances are weekly attracted by a magnet.

e) When a rod of Paramagnetic substance is suspended freely in a uniform magnetic field, the rod comes to rest with its axis parallel to the applied field.

f) Paramagnetism is generally exhibited by the elements due to the presence of unpaired electrons.

g) The reason is that an unpaired electron being lonely can spin in any direction ,i.e., it can assign its magnetic moment in either positive or negative direction. Due to this there will be unequal number of positive and negative spins and hence after the cancellation of the opposite spins there will be some residual magnetic moment . This is the reason why in a Paramagnetic substance, the individual atoms / molecules / ions have small net magnetic moment.

h) The Magnetic Susceptibility of a Paramagnetic substance have a small positive value.

i) The Relative Permeability of Paramagnetic substances is slightly greater than 1 .

j) Paramagnetic substances lose their magnetism as soon as the external magnetic field is removed.Thus the total magnetization drops to zero when the applied field is removed.

k) The Magnetization of the Paramagnetic substances decreases with the increase in temperature.

l) Paramagnetism is normally stronger than Diamagnetism .

m) Below the Curie temperature , certain Paramagnetic materials exhibit Ferromagnetism .

n) All the three states of matter exhibit Paramagnetism. eg :- Aluminium,Oxygen,Platinum.

Elements from the Periodic Table which exhibit Paramagnetism are :-
1) Lithium
2) Oxygen
3) Sodium
4) Magnesium
5) Aluminium
6) Calcium
7) Titanium
8) Manganese
9) Strontium
10) Zirconium
11) Molybdenum
12) Ruthenium
13) Rhodium
14) Palladium
15) Tin
16) Barium
17) Cerium
18) Neodymium
19) Samarium
20) Europium
21) Terbium
22) Dysprosium
23) Holmium
24) Erbium
25) Thulium
26) Tungsten
27) Osmium
28) Iridium
29) Platinum

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Friday, 20 July 2012

What is Diamagnetism ? Behaviour of Diamagnetic Substances & the Elements which exhibit Diamagnetism..!




Diamagnetism

a) The term Diamagnetism was coined by Michael Faraday in 1845 .

b) Those substances which when placed in a magnetic field, are weekly magnetised in a direction opposite to that of the magnetising field are called as Diamagnetic Substances .

c) When a Diamagnetic substance is placed in a non-uniform magnetic field , it's atoms acquire a small magnetic dipole moment in a direction opposite to that of the magnetic field .

d) As a result , the Diamagnetic substances moves from stronger part of the magnetic field to it's weaker part i.e. they are weakly repelled by the magnet .

e) The Diamagnetic substances do not retain their magnetic properties when the external magnetic field is removed.

f) Diamagnetism is usually observed in Solids composed of atoms with completely filled electronic shells .

g) The reason is that in a completely filled shell there are equal number of electrons with positive and negative spins, so that the total magnetic moment is zero .

h) This is the reason why the individual atoms in a Diamagnetic substance do not posses any net magnetic dipole moment.

i) The magnetic susceptibility of a Diamagnetic substance has a small negative value.

j) The relative permeability of a Diamagnetic substance is slightly less than 1.

k) The behaviour of a Diamagnetic substance is independent of temperature.

l) That is why Magnetic susceptibility of Diamagnetic substances do not change with temperature and hence the Diamagnetic substances do not obey Curie's Law .

m) The Diamagnetic substances when placed in a uniform magnetic field, they set their longest axis at right angles to the direction of the field and the shortest axis along the direction of the field.

n) Orbital motion of electrons is the root cause of magnetism in Diamagnetic substances.

o) All Substances are Diamagnetic to some extent .

Elements from the Periodic Table which exhibit Diamagnetism are :-
1) Hydrogen
2) Helium
3) Beryllium
4) Boron
5) Carbon
6) Nitrogen
7) Neon
8) Silicon
9) Phosphorus
10) Sulphur
11) Chlorine
12) Argon
13) Copper
14) Zinc
15) Gallium
16) Germanium
17) Arsenic
18) Selenium
19) Bromine
20) Krypton
21) Silver
22) Cadmium
23) Indium
24) Antimony
25) Tellurium
26) Xenon
27) Gold
28) Mercury
29) Thallium
30) Lead
31) Bismuth

Of this all elements Bismuth and carbon graphite are the strongest Diamagnetic materials.

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