Question

34. (a) In the periodic table, how does the tendency of atoms to lose electrons change on going from
(i) left to right across a period ?
(ii) top to bottom in a group?
(b) How does the size of atoms of elements vary down a group in the periodic table? Why is it so ?
(c)On the basis of electronic configuration, how will you identify the first and the last element of
a period ?​

Answer 1

The periodic trends are as follows.

• a).(i) When we move across a period from left to right, the tendency of the atoms to lose electrons decreases. This property is known as ionization potential. This is due to increase in nuclear charge.
• (ii) As we move down a group, the tendency to lose electrons or ionization potential of elements increases. This is due to increase in number of shells.
• b). The size of atoms increases when we move down a group. This is because the number of shells increase as we move lower and the distance between the outermost shell and nucleus is large.
• (c). According to the electronic configuration of elements, the first element of every period has its single valence electron occupying an s-shell. The last electrons of every period have a complete octet and no valence electrons.