Difference between a mixture and a compound?

Can someone me with questions 15 to 17 plz.

Cucl2 + 2nano3 cu(no3)2 + 2nacl what is the percent yield of nacl if 31.0 g of cucl2 reacts with excess nano3 to produce 21.2 g of nacl? 49.7% 58.4% 63.6% 78.7%

What happens to the atomic radius when an elctron is lost