Question

Elements with configuration 2, 8, 2 and 2, 7 are placed in modern periodic table. Find out:
1. the valency of the elements mentioned above.
2. the period and group of the above elements.

Answer 1

1. Element with electronic configuration 2, 8, 2 is magnesium and it has a valency of 2, as it is easy for Mg to lose 2 electrons and attain the nearest noble gas configuration.
Element with electronic configuration 2, 7 is fluorine and it has a valency of 1, as it can accept one electron and attain the nearest noble gas configuration.
2. Element with electronic configuration 2, 8, 2 belongs to 3rd period and 2nd group.
Element with electronic configuration 2, 7 belongs to 2nd period and 17th group.