Hint:The metals are the elements which release electrons to other atoms in the reaction to form a cation and the non-metal are the elements which gain electrons to form anion.
Complete step by step answer:
In the periodic table, the maximum chemical reactivity is at extreme left. In the left side of the periodic table alkali metals are present. The alkali metals are the most reactive metal among the other metal compounds. The metal tends to release its electrons in the reaction to form metal cation and has +1 oxidation state. The reactivity of the alkali metal is due to large atomic radii and low ionization energy. The atomic radii is the distance between the nuclei of two atoms which are joined with each other. Ionization energy is defined as the measure of the difficulty to remove the electrons from the atom. On the ride side of the periodic table, a halogen group is present. The reactivity of the halogen is due to high negative electron gain enthalpy. The halogen atom gains electrons to form anion. The electron gain enthalpy is the amount of energy released on accepting the electrons by the neutral gaseous atom to form an anion.
Thus, least ionization enthalpy on the left and highest negative electron gain enthalpy on the right are the two properties shown by alkali metal and halogen atom of the periodic table.
Therefore, the correct option is A.
The atomic radius increases on moving down in the group and decreases on moving left to right in the period. Ionization energy increases from moving left to right in period and decreases on moving down in the group.