Question

An element X belongs to the 3rd period and group 2 of the periodic table. State:
(a) The number of valence electrons
(b) The valency
(c) Whether it is metal or non-metal

Answer 1

The element which belongs to group 2 and period 3 will be magnesium. Its electronic configuration is $\text{1}{{\text{s}}^{2}}\text{2}{{\text{s}}^{2}}\text{2}{{\text{p}}^{6}}\text{3}{{\text{s}}^{2}}$. The element belongs to s-block. The atomic number of the element is 12 and atomic mass is 24. It is a metal. It shows metallic properties like lustre and shiny appearance. Relate the valence electrons with group number given.

Complete step by step solution:
Let us find the valency and valence electrons of the element which belongs to group 2 and period 3:
-The element belongs to group 2. The group to which an element belongs is equal to the number of valence electrons. It means that the valence electrons in the element are 2. After losing two electrons, the element will achieve the inert gas configuration.
-The number of valence electrons is equal to the valency of the element. Valency is always positive. So, the valency of the element is +2.
-The elements belonging to group1 and group 2 are all metals only. This element belongs to group 2, so it will be metal.

Additional information:
Applications of magnesium:
(1) It is used to form products such as laptops, car seats, cameras as magnesium is a light-weight element.
(2) It is added to molten steel and iron to remove sulphur.

Note: It is not always that valency equal to the number of valence electrons. There are differences between valence electrons and valency-
The valence electrons of fluorine are 7. But the valency of fluorine is +1. As fluorine needs one electron to achieve the inert gas configuration.