Your understanding before wasn't quite right. The ionizing in ionizing radiation is the key, its about knocking off an electron to form an ion. So that's someth

Your understanding before wasn't quite right. The ionizing in ionizing radiation is the key, its about knocking off an electron to form an ion. So that's something like a UV photon exciting an electron and breaking a covalent chemical bond. Hydrogen bonds are weaker electrostatic interactions between molecules where the charge is distributed in two molecules such that they have a weak + and - charge arrangement. So pure water for example, the hydrogens from one molecule have a bit more + and the oxygen has a bit more - within each molecule. If you think about how that works with a bunch of magnets fixed on a peg board they all try and match up their N and S if you move one they all wobble around to find a new arrangement to minimise the energy across the board. Thats hydrogen bonding all the H and O between different molecules try and match their charges. In DNA there are either 2 or 3 of those kinds of bonds to match up. Covalent bonds are more like how the magnets are fixed on the peg board. So if you split a magnet off its way more chaos right? That magnet will fly off and stick to another one and all bets are off on how everything else will interact.