Question

In the preparation of amorphous silicon, $HF$ is used to remove
(A) $Mg$
(B) $Si{{O}_{2}}$
(C) $Si$
(D) None of these

Answer 1

Allotropes are known by different forms of chemical elements in the same physical state in which these elements are bonded in different manners. There are two allotropes of silicon: Amorphous silicon and crystalline silicon

Complete Step by step explanation:
-Silicon is a chemical element represented by the symbol Si having atomic number 14. It is a member of group 14 in the periodic table. Electronic configuration is represented by $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{2}}$. Amorphous silicon is a non crystalline form of silicon used for solar cells and thin film transistors in LCDs. It is a powdery substance which is brown in color. The atoms in the structure are mostly connected throughout, but some atoms are not bonded to their maximum capacity. It is one of the most reactive silicon forms.
-$HF$ is known by hydrogen fluoride it is used in medicines and polymers formation. It is a very dangerous gas that can cause blindness by rapid destruction of the corneas. In the preparation of amorphous silicon hydrogen fluoride $HF$ is used to remove leftover silica ($Si{{O}_{2}}$).
$Si{{O}_{2}}+4HF\to Si{{F}_{4}}+2{{H}_{2}}O$

Hence, b is the right option.

Note: Amorphous silicon differs from other allotropic models such as monocrystalline silicon—a single crystal, and polycrystalline silicon, that consists of small grains, also known as crystallites.