Home
Class 12
CHEMISTRY
Ionic solids, which have anioninc vacanc...

Ionic solids, which have anioninc vacancies due to metal excess defect, developed colour. Explain with the help of a suitalbe example.

Text Solution

Verified by Experts

Let us illustrate by sodium choride `(Na^(+)Cl^(-))` crystals. Upon heating in the atmosphere of sodium (Na) vapours, sodium atoms get deposited on the surface of the crystals. The `Cl^(-)` ions from the crystal lattice leave their sites ans diffiuse into the surface. They tend to combine with sodium atoms present in the vapouus which in turns get ionised to form `Na^(+)` ions by releasing electrons. The latter are trapped by the anionic vacancies created by `Cl^(-)` ions in order to maintain the crystals electrically neutral. Now, the electrons absorb radiations corresponding to a certain colour from white light and start vibrating. They emit radiations corresponding to yellow colour. That is how, the crystals of sodium chloride develop yellow colour. These electrons are called F-centres because these are responsible for colours (In German. F = Farbe meaning colour).
Promotional Banner

Similar Questions

Explore conceptually related problems

Metal excess defect arises due to

One of the main objective of biotechnology is to minimize the use of insecticides on cultivated crops. Explain with the help of a suitable example how insect resistant crops have been developed using techniques of biotechnology.

What is the point defect due to the presence of foreign atom ? Explain with suitable example.

Why do hermaphrodite angiosperms develop out breeding devices? Explain any two such devices with the help of examples.

Explain the reactions of water with metals with the help of examples.

Define isotopes why do isotopes have same atomic number but differente mass numbers? Explain with the help an example.

Define isotopes why do isotopes have same atomic number but differente mass numbers? Explain with the help an example.

Assertion: p-type semiconductors are good conductors of electricity due to metal excees defects Reason: f-centres are created due to metal excess defects

Statement-1:p-type semiconductor are good conductor of electricity due to metal excess defect. Statement-2: F-centres are created due to metal excess defect.

Name the organism from which the 'cry' genes are isolated. Mention with the help of suitable example why and how bio-technologists have made use of 'cry' genes.