Hydrogen - Hydrides

Hydrides are binary compounds formed when hydrogen reacts with almost all elements except noble gases, represented by the general formula $EH_x$ or $E_mH_n$.

Ionic or Saline Hydrides are formed by highly electropositive s-block elements (alkali and alkaline earth metals). Examples include $LiH$, $NaH$, and $CaH_2$. They are stoichiometric, high-melting crystalline solids that conduct electricity in the fused state.

Covalent or Molecular Hydrides are formed by p-block elements. They are classified based on the number of electrons and bonds in their Lewis structure: Electron-deficient (e.g., $B_2H_6$), Electron-precise (e.g., $CH_4$), and Electron-rich (e.g., $NH_3$, $H_2O$, $HF$).

Metallic or Interstitial Hydrides are formed by many d-block and f-block elements. They are usually non-stoichiometric, such as $LaH_{2.87}$, $YbH_{2.55}$, and $TiH_{1.5-1.8}$. Hydrogen atoms occupy interstitial sites in the metal lattice.

Ionic hydrides react violently with water to produce hydrogen gas: $NaH(s) + H_2O(l) \rightarrow NaOH(aq) + H_2(g)$.

Complex hydrides like Lithium Aluminium Hydride ($LiAlH_4$) and Sodium Borohydride ($NaBH_4$) are powerful reducing agents used in organic chemistry.