The Durkin Opening (also known as the Durkin Attack or the Sodium Attack) is a rarely played chess opening beginning with the move: 1. Na3
The Durkin Opening is named for Robert James Durkin (1923–?) of New Jersey. The name "Sodium Attack" comes from the algebraic notation 1.Na3, as Na is the chemical symbol for the element sodium.
This awkward development of the queen's knight does little to utilize White's advantage of the first move. From a3 the knight does not influence the center or possess much activity. It is likely that White will move this knight again soon, perhaps by playing c4 and either recapturing on c4 (e.g. 1...d5 2.c4 dxc4 3.Nxc4) or playing Nc2. If this is White's plan, it is stronger to play 1.c4 (the English Opening). As such, this opening is probably most valuable as a way to avoid opening preparation. On the other hand, there are better ways to avoid an opponent's opening preparation, for example by developing the b1-knight to c3.
The Durkin Opening has several named variations:
1...e5 2.Nc4 Nc6 3.e4 f5 (Durkin's Gambit)
1...e5 2.d3 Bxa3 3.bxa3 d5 4.e3 c5 5.Rb1 (Celadon Variation)
1...g6 2.g4 (Chenoboskian Variation)