Question

The electronic configuration of an element X is 2, 8, 18 7 to which group and Period of the modern periodic table does X belongs state its valency and justify your answer in each case

Answer 1

Answer:

1 . Since ‘X’ has three energy shells and period number of an element is equal to the number  of energy shells, X belongs to 4rd period.

2 . X has 7 valence electrons it belongs to group 17.

3.  Valency will be 1. To acquire noble gas configuration it will gain 1 electrons.

Answer 2

The element belongs to the 4th period.

• he electronic configuration of the element X is
• ${1s}^{2} {2s}^{2} {2p}^{6} {3s}^{2} {3p}^{6} {4s}^{2} {3d}^{10} {4p}^{5}$
• Thus its valance shell is 4p orbital.
• Its valency is 7 as two electrons are present in 4s orbital and five electrons are present in 4p orbital.
• The total number of electrons of X is 35. Thus it is Bromine and belongs to the 4th period.
• It is an element of the halogen family of group 17.