Valency is the number of electrons present in the outermost shell.
I feel like I know this but I just can't answer it, sorry
0.500 grams would be left after 56.0 days.
After 14 days=4.00 g
After 28 days=2.00 g
After 42 days=1.00 g
After 56 days=0.500 g
This is after four half lives.
