Question

Write the electronic configuration and valency of the following 1) chlorine
2) sodium
3) silicon

Answer 1

1. Chlorine (Cl)
  Electronic configuration : 2, 8 7
                      Valency       : 1

2. Sodium (Na)
   Electronic configuration :2,8,1
                              Valency: 1

3. Silicon(Si)
    Electronic configuration :2,8,4
                             Valency :2

Answer 2

Electronic configuration of elements is the representation of the number of electrons present in the orbits of the atom. Valency is the number of electrons present in the outermost orbit of the atom.

Explanation:

Electronic configuration of chemical elements is the representation of the number of electrons present in the orbits of the atom.  

Valency is the number of electrons present in the outermost orbit of the atom. The electrons present in the highest occupied orbit (last orbit) determine the stability and reactive nature of an element.

• Chlorine

The atomic number of chlorine is 17, it is a Halogen. Its electronic configuration is 1s²2s²2p⁶3s²3p⁵. The valency of chlorine is 7, there are 7 electrons present in the outermost orbit hence they are highly reactive elements.

• Sodium

The atomic number of sodium is 11, it is a alkali metal. Its electronic configuration is 1s²2s²2p⁶3s¹. The valency of sodium is 1, there is only electron present in the outermost orbit. They are highly reactive elements when exposed to air and water hence are stored in kerosene.

• Silicon

The atomic number of silicon is 14, it is a metalloid. Its electronic configuration is 1s²2s²2p⁶3s²3p². The valency of silicon is 4, there are 4 electrons present in the outermost orbit. They are reactive than germanium.