The　cycloadditions　of　21　singlet　substituted　carbenes,　silylenes,　and　germylenes　onto　the　diamond　(100)　surface　have　been　theoretically　studied　by　means　of　density　functional　theory　coupled　with　effective　cluster　models.　The　calculated　reaction　energies　and　reaction　pathways　have　disclosed　that　the　substituents　play　an　important　effect　on　the　reaction　profiles　for　the　additions　of　carbenes,　silylenes,　and　germylenes　onto　the　diamond　(100)　surface.　Our　theoretical　investigations　illustrate　that,　irrespective　of　carbenes,　silylenes,　and　germylenes,　the　cycloadditions　of　those　with　electropositive　substituents　(such　as　H　and　CH3)　onto　diamond　(100)　are　much　more　favorable　than　those　with　electronegative　and　π-donating　substituents　(such　as　F　and　NH　2)　both　thermodynamically　and　kinetically.　In　broad　perspective,　we　believe　that　a　similar　reactivity　trend　can　also　be　extended　to　that　of　Si　(100),　Ge　(100),　fullerene,　single-walled　carbon　nanotube,　disilenes,　digermenes,　silenes,　and　germenes　because　all　of　these　materials　feature　an　analogous　bonding　motif.　©　2006　American　Chemical　Society.