New Concepts/Shortcuts 23 Flashcards
eg of non stoichiometric defects?
metal excess defect and metal deficiency defect
which kind of metals show metal excess defect?
Alkali halides like NaCl and KCl show this type of defect.
what happens in metal excess defect die to anionic vacancies?
When crystals of NaCl are heated in an atmosphere of sodium vapour, the sodium atoms are deposited on the surface of the crystal. The Cl– ions diffuse to the surface of the crystal and combine with Na atoms to give NaCl.
This happens by the loss of electrons by sodium atoms to form Na+ ions. The released electrons diffuse into the crystal and occupy anionic sites.
As a result the crystal now has an excess of sodium. The anionic sites occupied by unpaired electrons are called F-centres
what color is imparted on NaCl due to metal excess defect?
They impart a yellow colour to the crystals of NaCl.
what makes lithium crystals pink and excess of potassium violet(or lilac)?!
excess of lithium makes LiCl crystals pink and excess of potassium makes KCl crystals violet (or lilac).
whats metal excess defect due to the present of extra cations at interstitial sites?
Zinc oxide is white in color at room temperature. On heating, it loses oxygen and turns yellow.
whats the conductivity in the intermediate range!?
conductivities in the intermediate range from 10^–6 to 10^-4 ohm^–1 m^–1.
the electrical conductivity of semiconductor increases with _______ in temperature
the electrical conductivity of semiconductor increases with true in temperature
which oxides behave like metal in conductivity!?
TiO, CrO2 and ReO3 behave like metals.
which oxide is like metallic copper in its conductivity and appearance?
Rhenium oxide, ReO3 is like metallic copper in its conductivity and appearance.
which oxides show metallic or insulating properties depending on temperature?
Certain other oxides like VO, VO2, VO3, and TiO3 show metallic or insulating properties depending on temperature.
eg of ferromagnetic materials?
A few substances like iron, cobalt, nickel, gadolinium and CrO2 are attracted very strongly by a magnetic field.
eg of antiferromagnetism?
MnO showing antiferromagnetism have domain structure similar to ferromagnetic substance, but their domains are oppositely oriented and cancel out each other’s magnetic moment
whats ferrimagnetism?
Ferrimagnetism is observed when the magnetic moments of the domains in the substance are aligned in parallel and anti-parallel directions in unequal numbers . They are weakly attracted by magnetic field as compared to ferromagnetic substances.
These substances also lose ferrimagnetism on heating and become paramagnetic
eg of ferrimagnetic materials
Fe3O4 (magnetite) and ferrites like MgFe2O4 and ZnFe2O4 are examples of such substances.
