What are the periods and groups in a periodic table? Give two characteristics of each. (b) In terms of electronic configurations, explain the variation in the size of the atoms of the elements belonging to the same period and same group. (c) Given alongside is a part of the periodic table. As we move vertically downward from Li to Fr: Li Be Na K Rb Cs Fr Ra (i) What happens to the size of atoms? (ii) What happens to their metallic character? (d) Name two properties of elements whose magnitudes change when going from top to bottom in a group of the periodic table. In what manner do they change? (e) Rewrite the following statement after correction, if necessary: Groups have elements with consecutive atomic numbers.

• The horizontal rows of elements in a periodic table are called Characteristics:
  • The elements in a period have consecutive atomic
  • The of elements in period is fixed by the maximum no. of electrons which can be accommodated in various shells.

The vertical columns in a periodic table are called groups. Characteristics:

• The elements in a group do not have consecutive atomic
• All the elements in a group have similar electronic configurations and show similar
• The size of the atom increases on moving from top to bottom in the same group due to the adding up of shells at each step.

In a period the size of the atom decreases across the period because the atomic number increases. Therefore the number of electrons and protons increases, nuclear charge increases and the electrons will held even tighter.

(c)(i) The size of the atom increases. (ii)The metallic character also increases.

(d) On moving down the group, the atomic size and metallic character increases. As we move down

from top to bottom the size of atom increases from lithium to francium.

In alkali metals of group 1, lithium is the least metallic element whereas francium is the most metallic element