Question

The element below sodium in the same group would be expected to have a __________ (lower/higher) electro-negativity than sodium and the element above chlorine would be expected to have a __________ (lower/higher) ionization potential than chlorine.
(Choose the word or phrase from the brackets which correctly completes the following statement)

Answer 1

In the same group, electro-negativity as well as ionization potential decreases as we go down the same group because atomic size increases and nuclear charge decreases i.eThe first element will have the highest value of electro-negativity and ionization potential and the last element will have least value of electro-negativity and ionization potential along the same group.

Complete step by step answer:
We will split the given statement into two parts:
The property of an atom to attract electrons towards itself when it is combined in a compound is called electro-negativity. It decreases with the increase in atomic size of the element and vice-versa. It increases with the increase in nuclear charge of the atom and vice-versa. The atomic size increases as we go down the group in a periodic table as an extra shell of electrons is added to the new elements in each group. Hence, electro-negativity decreases with the increase in atomic size in each group. Thus, the element i.e., potassium below sodium in the same group would be expected to have a lower electro-negativity than sodium.
The energy required to remove an electron from an isolated gaseous atom and thereby converting it into a positively charged ion is called ionisation energy or ionisation potential. It decreases with the increase in atomic size of the element and increases with the increase in nuclear charge of the atom. As we go down the group, ionization potential decreases as electrons are loosely held due to increase in size and hence require less energy for their removal. Hence, the element i.e., fluorine above chlorine would be expected to have a higher ionization potential than chlorine. Also, the nuclear charge on fluorine is more than chlorine and thus more energy is required i.e, more ionization potential to pull out the electrons from the valence shell.

Note: Both electro-negativity and ionization potential decreases down the same group and vice-versa i.e., as we go down the group electro-negativity and ionization potential decreases with the increase in atomic size and decrease in nuclear charge or nuclear pull.