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Group 1 elements (Li, Na, K, Rb, Cs, Fr) have [noble gas] $ns^1$ configuration. They are the largest atoms in their periods with the lowest IE, which decreases down the group (Li: 520 → Cs: 376 kJ/mol). Always +1 oxidation state. Strongest metallic reducing agents.

Key trends down the group: atomic radius increases, IE decreases, electronegativity decreases, metallic character increases, reactivity with water increases (Li slow → Cs explosive). All stored under kerosene (react with O2 and moisture).

Reducing power in aqueous solution: Li is strongest ($E^0$ = -3.04 V) despite highest IE. This paradox is resolved by $Li^+$'s exceptionally high hydration energy (-519 kJ/mol) due to its very small size — the hydration energy overcompensates the IE.

Flame test colours arise from thermal excitation of the $ns^1$ electron: Li (crimson), Na (golden yellow, intense), K (violet, masked by Na — view through cobalt blue glass), Rb (red-violet), Cs (blue).

In liquid NH3, alkali metals dissolve forming solvated electrons: Na → $Na^+$(ammoniated) + $e^-$(ammoniated). The solvated electrons give deep blue colour, paramagnetism, and strong reducing power. At higher concentrations, the solution turns bronze (electrons pair up, diamagnetic). Birch reduction uses these solutions.