Question

The colour of pure silicon in crystalline form is:
Brown
Grey
Black
Yellow

Answer 1

Hint: Every element obtained in the nature has some properties such as its colour, structure, reactivity, etc. In single crystal silicon atom, the crystalline framework is homogeneous in nature, which can be recognized by an even external colouring. Crystalline silicon is a lustrous, greyish-black coloured element and the amorphous form is a dark brown coloured powder.

Complete step-by-step answer:
Silicon is a non-metallic chemical element in the carbon family i.e. Group 14 of the periodic table. Silicon is the second most abundant element in the crust that makes up 27.7 percent of Earth’s crust on being surpassed only by oxygen. Pure silicon is too reactive to be found in nature yet it is found in all rocks, sand, clays, and soils, combined either with oxygen as silica or with oxygen and other elements as silicates. Its compounds also occur in all natural water bodies, in the atmosphere, in many plants, in the skeletons, tissues, and body fluids of some animals.
We can see that in compounds, silicon dioxide occurs both in crystalline minerals such as quartz, cristobalite, tridymite and amorphous or seemingly amorphous minerals in all land areas. Pure silicon is a hard, dark grey solid with a metallic lustre and has an octahedral crystalline structure similar to that of the diamond form of carbon, to which silicon shows many chemical and physical similarities.

The reduced bond energy in crystalline silicon leaves the element with lower melting, softer, and chemically more reactive than diamond. Whereas an amorphous form of silicon is brown coloured solid and has a microcrystalline structure.

Additional information: Crystalline silicon is an alloying agent in iron and aluminium, in the production of silicones, an addition to ceramics, welding rods, powder metallurgy, etc. Crystalline silicon metal is important to the electronic industry as well. It is the base material used in the manufacture of high purity polycrystalline silicon and the products are used in the manufacture of semiconductors, microchips for computers and solar cells which are used to capture electrical energy from the sun.
Hence, the correct option is (B).

Note: Crystalline silicon can be used to produce ultra-pure silicon wafers which are used in the semiconductor industry, in electronics and in photovoltaic applications. We can dope an ultra-pure silicon with other elements to adjust its electrical response by controlling the number and positive and negative charge of current carriers.