Question

Write the chemical formula of the compound formed when boron reacts with chlorine.
[Atomic weight of Boron =5]
A.BCl
B.$BC{l_2}$
C.$BC{l_3}$
D.$BC{l_5}$

Answer 1

Boron is basically a chemical element with the symbol B and atomic number 5. It is a low abundant element that is found in the earth’s crust and solar system. Moreover, chlorine is the second lightest halogen and is represented by the symbol Cl. It basically appears as a pale-yellow green gas.

Complete step by step answer:
First of all, we will discuss the properties of boron and chlorine. Basically, boron is a chemical element with atomic number 5. It is further a poor conductor of electricity and has several forms. It forms borides when it reacts with water. It belongs to the ${13^{th}}$ group of the p block elements and all the elements of this group are metallic in nature except boron which is a metalloid. These elements generally exhibit two oxidation states i.e. +3 and +1.
Now chlorine is placed between fluorine and bromine in the periodic table. It is a chemical element with atomic number 17 and symbol Cl. This element is basically less reactive than fluorine but more reactive than bromine. Moreover, in comparison the chloride ion is a weaker reducing agent than bromine ion but is stronger than fluoride.
Now, the electronic configuration of boron is $1{s^2}2{s^2}2{p^1}$. It has three electrons in the outermost shell and hence, it can form three covalent bonds. So, it forms $BC{l_3}$ i.e. boron trichloride with chlorine.

Hence, option C is correct.

Note: Boron trichloride is a colorless gas and is a reagent in organic synthesis. It is highly reactive towards water. Further it has a melting and boiling point of $- {107.3^ \circ }C$ and ${12.6^ \circ }C$ respectively. The central boron atom in this compound is electron deficient and thus enables the molecule to accept additional pairs of electrons and further acts as a Lewis base.