How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?

(a) Why did Mendeleev have gaps in his periodic table ? (b) State any three limitations of Mendeleev's classification ? (c) How does electronic configurations of atoms change in a period with increase in atomic number?

The atomic radii of the elements across the second period of the periodic table -

How does electronic configuration of atoms change within a period, with increase in atomic number ?

What is a period in a periodic table ? How does the electronic configuration change in a period with increase in atomic number from left to right ?

Write the electronic configuration of second element of group VI-A of the periodic table.