In which of the following options order of arrangement does not agree with the variatioin of property indicated against it?
Thinking process.
i) The ionic size increases as the positive charge on the cation decreases or the negative charge on the anion increases.
ii) First ionisation enthalpy increases from left to right in the periodic table.
iii) Electron gain enthalpy increases as the electronegativity of the atom increases.
iv) The metallic character increases as the size of the metal atom increases.

Options

A. `Al^(3+) lt Mg^(2+) lt Na^(+) lt F^(-)` (Increasing ionic size)
B. `BltCltNltO` (Increasing first ionisation enthalpy)
C. `IltBrltClltF` (Increasing electron gain enthalpy)
D. `Li lt Na lt K lt Rb` (Increasing metallic radius)

Answer

B, C

Explanation

(b,c) Due to greater stability of the half filled electronic configuration of nitrogen, its ionisation enthalpy is higher than that of oxygen. Thus, option (b) is incorrect.
Due to stronger electron-electron repulsions in the small size of flourine the negative electron gain enthalpy of fluorine is lower than that of chlorine. Hence, option (c) is incorrect.