This Celtic symbol of everlasting love is formed from two triskeles. The triskeles, three cornered knots, denote the three aspects of two people, body, mind and spirit. The two triskeles, joined together, show a circle, the everlasting circle of eternity.
All the others are weak acids. A strong acid is one that dissociates completely when it dissolves in water. Dissociate means that the substance splits apart into ions. There are only a few strong acids in water, they are: HBr, HCl, HI, HNO3, HClO4 and H2SO4 (for the first H only) All other acids are weak acids. Chemists use the term strong or weak with regard to acids and bases to tell how much the substance dissociates in water.
What you have to realize about many of the lighter gaseous elements like oxygen, nitrogen, and fluorine, is that they have lone pair electrons that tend to be very repulsive. That is why the fluorine-fluorine bond is so weak. Actually, at least compared to fluorine, the oxygen-oxygen bond is surprisingly strong. Really the question you should be asking is why the oxygen-oxygen bond is not weaker than it is.