Anomalous Behavior of Lithium

Lithium shows anomalous behavior compared to other Group 1 metals due to:

Property	Lithium (Anomalous)	Other Alkali Metals (Normal)
Oxide type (excess $O_{2}$ )	$Li_{2}O$ (normal oxide only)	Na → peroxide; K,Rb,Cs → superoxide
Carbonate stability	$Li_{2}CO_{3}$ decomposes on heating → $Li_{2}O$ + C $O_{2}$	$Na_{2}CO_{3}$ , $K_{2}CO_{3}$ are thermally stable
Nitrate decomposition	$LiNO_{3}$ → $Li_{2}O$ + N $O_{2}$ + $O_{2}$ (like Mg( $NO_{3}$ )_{2})	M $NO_{3}$ → MN $O_{2}$ + $O_{2}$ (nitrite)
Bicarbonate	No stable solid $LiHCO_{3}$ (only in solution)	$NaHCO_{3}$ , $KHCO_{3}$ exist as stable solids
Chloride character	LiCl is covalent (soluble in organic solvents)	NaCl, KCl are ionic (insoluble in organic solvents)
Reaction with $N_{2}$	Li + $N_{2}$ → $Li_{3}N$ (at room temp)	Other alkali metals do NOT react with $N_{2}$
Diagonal relationship	Li ~ Mg (similar charge density)	No equivalent relationship

Diagonal relationship Li-Mg: $Li^{+}$ (small, +1) ≈ $Mg^{2+}$ (larger, +2) in charge density → similar behavior.