Atoms and the Periodic Table Crossword Puzzle

QUESTIONS LIST: nucleus : part of the atom comprising protons and neutrons (7), oxidation : process that causes reactive metals to discolour in air (9), mass : protons and neutrons have a relative _ of 1 (4), boron : the only non-metal group 3 element (5), chemical symbol : h is the _ of hydrogen (8,6), argon : gas used to stop cs and rb from oxidising in storage (5), lithium : metal harder than sodium and in the same group (7), positive : protons have a _ charge (8), sodium : na is the chemical symbol for _ (6), fluorine : non-metal with a mass number of 19 (8), electrons : negatively-charged sub-atomic particles (9)