Question

One of the elements of group 13 was not known at the time when Mendeleev gave his periodic table. This element has some interesting/remarkable properties much different from other elements of this group. 

Now answer the following questions 

(i) Name the element which was not known when Mendeleev gave his periodic table. 

(ii) Mention its few interesting and remarkable properties. 

(iii) Give one use of this element.

Answer 1

(i) The element not known when Mendeleev gave his periodic table is gallium (Ga). 

(ii) Some of its remarkable properties are : 

(a) It has the greatest liquid range of all known elements. It can melt (303 K ) in your hand but it does not boil until the temperature reaches 2676 K. 

(b) Like water, gallium is one of the few known materials which expands upon freezing. 

(iii) The greatest use of gallium is in the preparation of semiconductor gallium arsenide (GaAs). Integrated circuits made up of GaAs have achieved operating speeds up to five times that of the fastest silicon chips currently available, & they will operate over a wider temperature range than silicon circuits. However, these advantages come at a price because As it is a volatile and toxic element and hence GaAs is difficult to make.