In many-electron systems, the interelectronic angle density A( 12 ) represents the probability density function for the interelectronic angle i j spanned by position vectors r i and r j of any two electrons to be 12 . It is shown that in general the interelectronic angle density A( 12 ) is expressed by a linear combination of Legendre polynomials P n (cos 12 ). Explicit formulas for the expansion coefficients are presented for atoms described by determinantal wave functions. The results are

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... ied to the 102 atoms He through Lr in their ground states within the Hartree-Fock framework, and the expansion coefficients as well as the average interelectronic angles ͗ 12 ͘ are reported.