Question

A group of elements in the periodic table are given below.
(Boron is the first member of the group and Thallium is the last)
Boron, Aluminium, Gallium, Indium, Thallium
Answer the following questions in relation to the above group of elements :
(d) The atomic number of boron is 5. Write the chemical formula of the compound formed when boron reacts with chlorine?

Answer 1

• The electronic configuration of Boron (B) is 2, 3. It can share or donate its 3 electrons to the other combining element thus, its valency is 3.
• The electronic configuration of Chlorine (Cl) is 2, 8, 7. It can accept 1 electron to complete its octet thus, its valency is 1.

Hence, Boron shares its 3 electrons with 3 atoms of chlorine.

Therefore, the chemical formula of the compound is $BC{l}_3$.