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Group 15 (N, P, As, Sb, Bi) has ns^{2np}^3. Nitrogen's anomalies define the group's chemistry.

Nitrogen forms very strong ppi-ppi triple bonds (N triple bond N = 946 kJ/mol), making N2 inert. No d-orbitals limits max covalence to 4 (NCl5 impossible; PCl5 exists). N shows OS from -3 to +5 with diverse oxides: N2O(+1), NO(+2, paramagnetic), N2O3(+3), NO2(+4, brown), N2O5(+5, anhydride of HNO3).

Phosphorus prefers single bonds: P4 (tetrahedral, 60-degree angles, strained, reactive). White P4 is pyrophoric (stored under water); red P is polymeric and stable. PCl5 is TBP in gas, ionic [PCl4]^+[PCl6]^- in solid.

Oxyacids of phosphorus are heavily tested. Basicity equals the number of P-OH bonds (NOT total H atoms): H3PO2 (1 P-OH, monobasic, strong reducer), H3PO3 (2 P-OH, dibasic, reducer), H3PO4 (3 P-OH, tribasic, not reducer). P-H bonds are non-ionisable but provide reducing capability.

The inert pair effect gives $Bi^{3+}$ dominance over $Bi^{5+}$. Bi2O5 is a strong oxidising agent. BiCl3 hydrolyses to BiOCl (bismuthyl chloride).

Bond angles of hydrides decrease down the group: NH3 (107.3) > PH3 (93.3) > AsH3 (91.8) > SbH3 (91.3) because larger atoms use more p-character, approaching 90 degrees.