If an element gains 1 electron, what charge will it have? +1

-1

+7

-7

Iknow the answer is a but i don't know why

Which characteristics can be used to differentiate star systems? check all that apply.

Oil rich countries in the middle east cover about 4% of earths total land area but prossess about 48% of the worlds known oil reserves what is the main reason for high concentration of reserves in this part of the world