Classification Of Elements And Periodicity In Properties

Factual questions

It is caesium and is an alkali metal .

The tendency of an atom to attract the bonding or shared pair of electrons towards its own side in a covalent bond is called electronegativity. It is a unitless quantity. Pauling scale and Mulliken scale are used to determine electro negativity. It increases in a period from left to right and decrease down a period. Fluorine is the most electronegative element of periodic table. ( according to pauling scale) Electron affinity and ionisation energy are expressed in and electron volt / atom

Generally, ionisation potential increases, as we move from left to right in a period. However, the ionisation potential of II group elements is higher than that of the III group elements. This is because of the fully filled -orbitals in II group elements. Hence, the correct order of ionisation potential is

As the size of atom decreases, a larger amount of energy is released when an electron is added to an isolated gaseous atom. Among the given species, the size of atom is smallest ( size of parent atom is smaller as compared to its anion), thus its electron affinity is highest. [Remember! the value of second electron affinity is generally positive. This is because, the second electron experience a greater force of repulsion from the existing electrons. Hence, to overcome this repulsion, some heat is absorbed. This is also the reason for lower electron affinity of as compared to .]