Atomic Puzzle XMas

Atomic Puzzle in Christmas style now! Clear each level by removing the atoms in the correct order. Can you predict the merging of the molecules so that there’s none left at the end of each level?

Use mouse to select combination of atoms.
1. The colour of the atom you click on does not matter.
2. Each combination must contain the same coloured atoms.
3. Only one atom can be left unpaired in each combination.