Question

please answer fast
whoevers answer first will be brainliest ​

Answer 1

21. helium

22. chemical reactivity

23. Blue

24. True( but there are exceptions )

25. double displacement

Answer 2

1) Helium

2) Reactivity series

3) Oxygen (or air) and an ignition source are required for combustion to occur. Hydrogen burns with a pale blue flame that is nearly invisible in daylight. The flame may appear yellow if there are impurities in the air like dust or sodium. A pure hydrogen flame will not produce smoke.

4) True

5) Displacement reaction

hope this will help you out......

and please do mark me as the brainlist