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Group 2 (Be, Mg, Ca, Sr, Ba, Ra) has [noble gas] $ns^2$ configuration. Compared to Group 1: smaller, denser, harder, higher m.p. (stronger metallic bonding from 2 valence electrons), higher IE. Always +2 OS.

Thermal stability of compounds increases down the group for carbonates, hydroxides, nitrates, and sulphates. The polarisation argument: small $M^{2+}$ (high charge density) distorts the electron cloud of large anions ($CO3^{2-}$, $NO3^-$, $OH^-$), weakening bonds and facilitating decomposition. BeCO3 decomposes at ~100 C; BaCO3 at ~1360 C.

Solubility trends (opposite for hydroxides vs sulphates):

• Hydroxides increase: Mg(OH)2 (insoluble) → Ba(OH)2 (soluble). For small $OH^-$, lattice energy falls faster than hydration energy.
• Sulphates decrease: MgSO4 (soluble) → BaSO4 (insoluble). For large $SO4^{2-}$, hydration energy falls faster than lattice energy.

Reactivity with water: Be (none) < Mg $\frac{hot water}{steam}$ < Ca (cold water) < Sr < Ba (vigorous). Flame colours: Ca (brick red), Sr (crimson), Ba (apple green). Be and Mg — none (IE too high).

Key compounds: CaO (quicklime), Ca(OH)2 (slaked lime), CaCO3 (limestone), CaSO4.2H2O (gypsum), CaSO4.1/2H2O (POP), MgSO4.7H2O (Epsom salt), BaSO4 (barium meal).