The hydride gap corresponds to elements of

Which of the following is radioactive?

Hydrogen behaves as an oxidising agent when it reacts with:

Assertion : Hydrogen combines with other elements by losing,gaining or sharing of electrons.
Reason : Hydrogen forms electrovalent and covalent bonds with other elements.

Arrange the following:
$(i)$ $CaH_{2}$,$BeH_{2}$,and $TiH_{2}$ in order of increasing electrical conductance.
$(ii)$ $LiH$,$NaH$,and $CsH$ in order of increasing ionic character.
$(iii)$ $H-H$,$D-D$,and $F-F$ in order of increasing bond dissociation enthalpy.
$(iv)$ $NaH$,$MgH_{2}$,and $H_{2}O$ in order of increasing reducing property.

The hydride ions $({H^{-}})$ are isoelectronic with