Question

(A). What is the functional difference in the electron configurations between the group $1$ and group $2$ elements?
(B). On the basis of electronic configuration, how will you identify the following: -
(i). Chemically similar electrons?
(ii). The first elements of a period.

Answer 1

Hint : The electronic configuration is the filling of the electrons of the atoms in the orbital and subshell determined by a few rules named, Hund's rule, Afbau rule, Paulie exclusion principle, and Bhor bury rule. All the elements obey these rules but few elements have exceptions in the filling of electrons such as copper, chromium.

Complete Step By Step Answer:
(A). The valence electrons are those electrons that are present in the valence shell. A valence shell is an outermost shell to which electrons are present. In the case of a group $1$ the elements have only $1$ electron in their valence shell, whereas in the case of a group $2$ the elements have $2$ electrons in their valence shell.
(B). The arrangement of the elements is done on the basis of their atomic number which is allotted on the basis of electronic configuration. Due to this electronic configuration, the elements have special characteristics.
(i). All the chemically similar elements will have the same valence electrons.
(ii). On the basis of electronic configuration, we can determine the first element of the period, as they have one electron in their valence shell.

Note :
While filling the electrons in the shells, try to remember all the electronic configuration laws namely Hund's rule, Afbau rule, Paulie exclusion principle, and Bhor bury rule. However, if via these laws the element does not attain stability they can have an exceptional configuration as copper and chromium has.