Respuesta :
Answer:
alll of them are possible, besides the last one
Explanation:
All of them are correct compounds besides the last one. The last one isn’t a correct compound because the second element does not exist
#NaO_2
- Impossible
- Na has valency 1 so O can never have 2 as subscript.
Correct compound=Na_2O
#MgCl_2
- Possible
- Valency of Mg is 2 and Cl is 1 so yes
#CaF
- Impossible
- Ca has valency 2 not 1
#NaBr
- Possible
- Na has valency 1 and Br has 1
#KHe
- Impossible
Helium is a noble gas so can't form compounds