One of the allotropic form of boron is `alpha -` rhombohedral boron. Number of faces and corners in its basic building `B_(12)` icosahedral unit are:

In crystalline form boron exists as Icosahedron that has x faces and y atoms linked in this unit. The value of (x-y) =

Boron exist in different allotropic forms. All allotropic form contains icosahedral units (icosahedral is regular shape with 12 corner & 20 faces) with boron atoms at all 12 corners and all bonds are equivalent. Calculate heat evolved at constant pressure (in KJ) per mole of boron atoms undergoing above change it DeltaH_(BE)(B-B) =200 KJ//"mol" . Report you answer after dividing by 100

Boron exist in different allotropic forms. All allotropic form contains icosahedral units (icosahedral is regular shape with 12 corner & 20 faces) with boron atoms at all 12 corners and all bonds are equivalent. Calculate heat evolved at constant pressure (in KJ) per mole of boron atoms undergoing above change it DeltaH_(BE)(B-B) =200 KJ//"mol" . Report you answer after dividing by 100

Among the following allotropic forms of sulphur , the number of allotropic forms , which will show paramagnetism is _________ (A) alpha -sulphur (B) beta -sulphur (C) S_2 - form

Which statement is incorrect? (1) Boron exist in many allotropic forms with B 12 icosahedral units (2) The most abundant metal is present in cyolite and bauxite (3) Gallium exist as a liquid metal on a warm day (4) Boron compounds are electron sufficient

Boron, the first member of group 13 (p-block) is a typical non-metal. H exists in two allotropic forms. The compounds of boron are mainly electron deficient as well as Lewis acids. For example, all the trihalides of boron (BX_(3)) are Lewis acids. The expected order of acidic strength based on the electro negativity of halogen atoms is : BF_(3)gtBC l_(3)gtBBr_(3)gtBl_(3) . But the actual order is the reverse. This is explained with the help of the concept of back bonding (p pi- p pi) . Among the hydrides of boron. diborane has a bridged structure. Which of the following statements of group 13, the one which is most acidic is:

Boron, the first member of group 13 (p-block) is a typical non-metal. H exists in two allotropic forms. The compounds of boron are mainly electron deficient as well as Lewis acids. For example, all the trihalides of boron (BX_(3)) are Lewis acids. The expected order of acidic strength based on the electro negativity of halogen atoms is : BF_(3)gtBC l_(3)gtBBr_(3)gtBl_(3) . But the actual order is the reverse. This is explained with the help of the concept of back bonding (p pi- p pi) . Among the hydrides of boron. diborane has a bridged structure. Among the halides of the elements of group 13, the one which is most acidic is:

Iron adopts two different crystalline allotropic forms one at 1183 K and other one below 1183 K, which differ in structural units as bcc and fcc are known as alpha and gamma forms.. What would be the ratio of densities of these two forms ( gamma and alpha ) ? Assume inter atomic distance remains same.