Which of the following have no unit?
Ionic radii vary in
An element belongs to 3rd period and group 13 of the periodic table. Which of the following properties will be shown by the element?
Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine?
Electron gain enthalply of F is less negative than that of Cl because when an electron is added to $F$, the added electron goes to the smaller $n=2$ quantum level and suffers repulsion from other electrons present in this level.
In case of Cl , the added electron goes to the larger $n=3$ quantum level and suffers much less repulsion from other electrons.
All transition elements are $d$ - block elements, but all $d$ - block elements are not transition elements. Explain.
Elements in which the last electron enters in the $d$-orbitals, are called $d$-block elements or transition elements. These elements have the general outer electronic configuration $(n-1) d^{1-10} n s^{0-2} . \mathrm{Zn}, \mathrm{Cd}$ and Hg having the electronic configuration $(n-1) d^{10} n s^2$ do not show most of the properties of transition elements.
The $d$-orbitals in these elements are completely filled in the ground state as well as in their common oxidation states. Therefore, they are not regarded as transition elements. Thus, on the basis of properties, all transition elements are $d$-block elements but on the basis of electronic configuration, all $d$-block elements are not transition elements.